Display device and electronic device

ABSTRACT

A display device with high design flexibility is provided. The display device includes a display element, a touch sensor, and a transistor between two flexible substrates. An external electrode that supplies a signal to the display element and an external electrode that supplies a signal to the touch sensor are connected from the same surface of one of the substrates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a display device. Oneembodiment of the present invention also relates to a method ofmanufacturing the display device.

Note that one embodiment of the present invention is not limited to theabove technical field. For example, one embodiment of the presentinvention relates to an object, a method, or a manufacturing method. Oneembodiment of the present invention relates to a process, a machine,manufacture, or a composition of matter. One embodiment of the presentinvention relates to a memory device, a processor, a driving methodthereof, or a manufacturing method thereof.

Note that in this specification and the like, a semiconductor devicegenerally means a device that can function by utilizing semiconductorcharacteristics. Thus, a semiconductor element such as a transistor or adiode and a semiconductor circuit are semiconductor devices. A displaydevice, a light-emitting device, a lighting device, an electro-opticaldevice, an electronic device, and the like may include a semiconductorelement or a semiconductor circuit. Therefore, a display device, alight-emitting device, a lighting device, an electro-optical device, anelectronic device, and the like include a semiconductor device in somecases.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on liquid crystal elements as a display element used in adisplay region of a display device. In addition, research anddevelopment have been extensively conducted on light-emitting elementsutilizing electroluminescence (EL). As a basic structure of theselight-emitting elements, a layer containing a light-emitting substanceis provided between a pair of electrodes. Voltage is applied to thislight-emitting element to obtain light emission from the light-emittingsubstance.

Light-emitting elements are a self-luminous element; thus, a displaydevice using the light-emitting elements has, in particular, advantagessuch as high visibility, no necessity of a backlight, and low powerconsumption. The display device using the light-emitting elements alsohas advantages in that it can be manufactured to be thin and lightweightand has high response speed.

A display device including the display elements can have flexibility;therefore, the use of a flexible substrate for the display device hasbeen proposed.

As a method of manufacturing a display device using a flexiblesubstrate, a technique has been developed in which a semiconductorelement such as a thin film transistor is manufactured over a substratesuch as a glass substrate or a quartz substrate, for example, thesemiconductor element is fixed to another substrate (e.g., a flexiblesubstrate) by using an organic resin, and then the semiconductor elementis transferred from the glass substrate or the quartz substrate to theother substrate (Patent Document 1).

In some cases, over a light-emitting element that has been formed over aflexible substrate, another flexible substrate is provided in order toprotect a surface of the light-emitting element or prevent entry ofmoisture or impurities from the outside.

Display devices are expected to be applied to a variety of uses andbecome diversified. For example, a smartphone and a tablet terminal witha touch panel are being developed as portable information terminals.

REFERENCE Patent Document

-   [Patent Document 1] Japanese Published Patent Application No.    2003-174153

SUMMARY OF THE INVENTION

In order to supply a signal or electric power to a display device usinga flexible substrate, it is necessary that part of the flexiblesubstrate be removed by a laser beam or an edged tool to expose anelectrode so that an external electrode such as a flexible printedcircuit (FPC) is connected to the electrode.

However, a method in which part of a flexible substrate is removed by alaser beam or with an edged tool has a problem in that an electrodeincluded in a display device is damaged easily and the reliability andmanufacturing yield of the display device are reduced easily. Inaddition, a display region and an electrode need to be provided with asufficient space therebetween in order to prevent damage to the displayregion due to the above-described method; for this reason, signalattenuation, electric power attenuation, or the like due to an increasein wiring resistance is caused easily.

An object of one embodiment of the present invention is to provide amethod of manufacturing a display device, which does not easily damagean electrode. Another object of one embodiment of the present inventionis to provide a method of manufacturing a display device, which does noteasily damage a display region. Another object of one embodiment of thepresent invention is to provide a highly reliable display device and amethod of manufacturing the display device. Another object of oneembodiment of the present invention is to provide a display device withhigh design flexibility and a method of manufacturing the displaydevice.

Another object of one embodiment of the present invention is to providea display device, electronic device, or the like having high visibility.Another object of one embodiment of the present invention is to providea display device, electronic device, or the like having high displayquality. Another object of one embodiment of the present invention is toprovide a display device, electronic device, or the like having highreliability. Another object of one embodiment of the present inventionis to provide a display device, electronic device, or the like that isunlikely to be broken. Another object of one embodiment of the presentinvention is to provide a display device, electronic device, or the likewith low power consumption. Another object of one embodiment of thepresent invention is to provide a display device, electronic device, orthe like with high productivity. Another object of one embodiment of thepresent invention is to provide a novel display device, electronicdevice, or the like.

Note that the descriptions of these objects do not disturb the existenceof other objects. In one embodiment of the present invention, there isno need to achieve all of these objects. Other objects will be apparentfrom and can be derived from the description of the specification, thedrawings, the claims, and the like.

One embodiment of the present invention is a display device including adisplay element and a touch sensor between two flexible substrates. Inthe display device, an external electrode that supplies a signal to thedisplay element and an external electrode that supplies a signal to thetouch sensor are connected from the same surface of one of thesubstrates.

One embodiment of the present invention is a display device including afirst substrate, a second substrate, a display element, a touch sensor,a first electrode, and a second electrode. The first substrate and thesecond substrate overlap with each other with the display element, thetouch sensor, the first electrode, and the second electrode positionedtherebetween. The first electrode supplies a signal to the displayelement. The second electrode supplies a signal to the touch sensor. Thefirst electrode and the second electrode are electrically connected toan external electrode through an opening in the second substrate.

An FPC can be used as the external electrode, for example. The externalelectrode includes a plurality of electrodes. The first electrode can beelectrically connected to some electrodes included in the externalelectrode. The second electrode can be electrically connected to otherelectrodes included in the external electrode. When the same potentialor signal is supplied to the first electrode and the second electrode,the first electrode and the second electrode can be electricallyconnected to an electrode included in the external electrode.

Another embodiment of the present invention is a display deviceincluding a first substrate, a second substrate, a display element, atouch sensor, a first electrode, and a second electrode. The firstsubstrate and the second substrate overlap with each other with thedisplay element, the touch sensor, the first electrode, and the secondelectrode positioned therebetween. The first electrode supplies a signalto the display element. The second electrode supplies a signal to thetouch sensor. The first electrode is electrically connected to a firstexternal electrode through a first opening in the second substrate. Thesecond electrode is electrically connected to a second externalelectrode through a second opening in the second substrate.

Another embodiment of the present invention is a display deviceincluding a first substrate, a second substrate, a display element, atouch sensor, a transistor, a first electrode, and a second electrode.The first substrate and the second substrate overlap with each otherwith the display element, the touch sensor, the transistor, the firstelectrode, and the second electrode positioned therebetween. The firstelectrode supplies a signal to the transistor. The transistor supplies asignal to the display element. The second electrode supplies a signal tothe touch sensor. The first electrode and the second electrode areelectrically connected to an external electrode through an opening inthe second substrate.

Another embodiment of the present invention is a display deviceincluding a first substrate, a second substrate, a display element, atouch sensor, a transistor, a first electrode, and a second electrode.The first substrate and the second substrate overlap with each otherwith the display element, the touch sensor, the first electrode, and thesecond electrode positioned therebetween. The first electrode supplies asignal to the transistor. The transistor supplies a signal to thedisplay element. The second electrode supplies a signal to the touchsensor. The first electrode is electrically connected to a firstexternal electrode through a first opening in the second substrate. Thesecond electrode is electrically connected to a second externalelectrode through a second opening in the second substrate.

One embodiment of the present invention can provide a method ofmanufacturing a display device that does not easily damage an electrode.Another embodiment of the present invention can provide a method ofmanufacturing a display device that does not easily damage a displayregion. Another embodiment of the present invention can provide a highlyreliable display device and a manufacturing method thereof. Anotherembodiment of the present invention can provide a display device withhigh design flexibility and a manufacturing method thereof.

One embodiment of the present invention provides a display device,electronic device, or the like having high visibility. One embodiment ofthe present invention provides a display device, electronic device, orthe like having high display quality. One embodiment of the presentinvention provides a display device, electronic device, or the likehaving high reliability. One embodiment of the present inventionprovides a display device, electronic device, or the like that isunlikely to be broken. One embodiment of the present invention providesa display device, electronic device, or the like with low powerconsumption. One embodiment of the present invention provides a displaydevice, electronic device, or the like with high productivity. Oneembodiment of the present invention provides a novel display device,electronic device, or the like.

Note that the description of these effects does not disturb theexistence of other effects. One embodiment of the present invention doesnot necessarily have all of these effects. Other effects will beapparent from and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are a perspective view and cross-sectional viewsillustrating one embodiment of the present invention.

FIGS. 2A and 2B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 3A and 3B are cross-sectional views each illustrating oneembodiment of the present invention.

FIGS. 4A to 4E illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 5A to 5C illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 6A and 6B illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 7A to 7D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 8A to 8D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 9A to 9D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 10A to 10C each illustrate an example of a pixel configuration ofone embodiment of a display device.

FIGS. 11A and 11B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 12A and 12B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 13A and 13B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 14A and 14B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 15A and 15B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 16A and 16B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 17A and 17B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 18A and 18B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 19A and 19C are perspective views and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 20A to 20C are a perspective view and cross-sectional viewsillustrating one embodiment of the present invention.

FIGS. 21A and 21B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 22A and 22B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 23A to 23C are perspective views and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 24A to 24D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 25A to 25D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 26A to 26D illustrate a manufacturing process of one embodiment ofthe present invention.

FIGS. 27A and 27B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 28A and 28B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 29A and 29B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 30A and 30B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 31A and 31B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 32A and 32B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 33A and 33B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 34A and 34B illustrate a manufacturing process of one embodimentof the present invention.

FIGS. 35A and 35B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 36A and 36B are a perspective view and a cross-sectional viewillustrating one embodiment of the present invention.

FIGS. 37A to 37C are a block diagram and circuit diagrams illustratingone embodiment of a display device.

FIGS. 38A1, 38A2, 38B1, and 38B2 are cross-sectional views eachillustrating one embodiment of a transistor.

FIGS. 39A1, 39A2, 39A3, 39B1, and 39B2 are cross-sectional views eachillustrating one embodiment of a transistor.

FIGS. 40A to 40C are a top view and cross-sectional views illustratingone embodiment of a transistor.

FIGS. 41A to 41C are a top view and cross-sectional views illustratingone embodiment of a transistor.

FIGS. 42A, 42B, 42C, 42D1, and 42D2 illustrate a structure example andan example of a driving method of a touch sensor.

FIGS. 43A to 43D illustrate a structure example and an example of adriving method of a touch sensor.

FIGS. 44A and 44B illustrate structure examples of light-emittingelements.

FIGS. 45A to 45F illustrate examples of electronic devices and lightingdevices.

FIGS. 46A and 46B illustrate an example of an electronic device.

FIGS. 47A to 47C illustrate an example of an electronic device.

FIGS. 48A to 48I illustrate examples of electronic devices.

FIGS. 49A and 49B illustrate an example of an electronic device.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to theaccompanying drawings. Note that the present invention is not limited tothe description below, and it is understood easily by those skilled inthe art that various changes and modifications can be made withoutdeparting from the spirit and scope of the present invention. Therefore,the present invention should not be construed as being limited to thedescription in the following embodiments. In the structures of thepresent invention to be described below, the same portions or portionshaving similar functions are denoted by the same reference numerals indifferent drawings, and explanation thereof will not be repeated.

The position, size, range, and the like of each component illustrated inthe drawings and the like are not accurately represented in some casesto facilitate understanding of the invention. Therefore, the disclosedinvention is not necessarily limited to the position, the size, range,and the like disclosed in the drawings and the like. For example, in theactual manufacturing process, a resist mask or the like might beunintentionally reduced in size by treatment such as etching, whichmight not be illustrated for easy understanding.

Especially in a top view (also referred to as a plan view), aperspective view, or the like, some components might not be illustratedfor easy understanding.

In this specification and the like, the term such as an “electrode” or a“wiring” does not limit a function of a component. For example, an“electrode” is used as part of a “wiring” in some cases, and vice versa.Furthermore, the term “electrode” or “wiring” can also mean acombination of a plurality of “electrodes” and “wirings” formed in anintegrated manner.

Note that the term “over” or “under” in this specification and the likedoes not necessarily mean that a component is placed “directly on” or“directly below” and “directly in contact with” another component. Forexample, the expression “electrode B over insulating layer A” does notnecessarily mean that the electrode B is on and in direct contact withthe insulating layer A and can mean the case where another component isprovided between the insulating layer A and the electrode B.

Functions of a source and a drain might be switched depending onoperation conditions, for example, when a transistor having oppositepolarity is employed or the direction of current flow is changed incircuit operation. Thus, it is difficult to define which is a source ora drain. Accordingly, the terms “source” and “drain” can be switched inthis specification.

Note that in this specification and the like, the expression“electrically connected” includes the case where components areconnected through an “object having any electric function”. There is noparticular limitation on an “object having any electric function” aslong as electric signals can be transmitted and received betweencomponents that are connected through the object. Accordingly, even whenthe expression “electrically connected” is used in this specification,there is a case in which no physical connection is made and a wiring isjust extended in an actual circuit.

In this specification, a term “parallel” indicates that the angle formedbetween two straight lines is greater than or equal to −10° and lessthan or equal to 10°, and accordingly also includes the case where theangle is greater than or equal to −5° and less than or equal to 5°. Aterm “perpendicular” indicates that the angle formed between twostraight lines is greater than or equal to 80° and less than or equal to100°, and accordingly also includes the case where the angle is greaterthan or equal to 85° and less than or equal to 95°.

In this specification, in the case where an etching step is performedafter a lithography process, a resist mask formed in the lithographyprocess is removed after the etching step, unless otherwise specified.

A voltage usually refers to a potential difference between a givenpotential and a reference potential (e.g., a source potential or aground potential (a GND potential)). A voltage can be referred to as apotential and vice versa.

Note that an impurity in a semiconductor refers to, for example,elements other than the main components of the semiconductor. Forexample, an element with a concentration lower than 0.1 atomic % can beregarded as an impurity. When an impurity is contained, the density ofstates (DOS) in a semiconductor may be increased, the carrier mobilitymay be decreased, or the crystallinity may be decreased, for example. Inthe case where the semiconductor is an oxide semiconductor, examples ofan impurity which changes characteristics of the semiconductor includeGroup 1 elements, Group 2 elements, Group 13 elements, Group 14elements, Group 15 elements, and transition metals other than the maincomponents of the oxide semiconductor; specifically, there are hydrogen(included in water), lithium, sodium, silicon, boron, phosphorus,carbon, and nitrogen, for example. In the case of an oxidesemiconductor, oxygen vacancies may be formed by entry of impuritiessuch as hydrogen. In the case where the semiconductor is silicon,examples of an impurity which changes characteristics of thesemiconductor include oxygen, Group 1 elements except hydrogen, Group 2elements, Group 13 elements, and Group 15 elements.

Note that ordinal numbers such as “first” and “second” in thisspecification and the like are used in order to avoid confusion amongcomponents and do not denote the priority or the order such as the orderof steps or the stacking order. A term without an ordinal number in thisspecification and the like might be provided with an ordinal number in aclaim in order to avoid confusion among components. A term with anordinal number in this specification and the like might be provided witha different ordinal number in a claim. Moreover, a term with an ordinalnumber in this specification and the like might not be provided with anyordinal number in a claim.

Note that in this specification, the channel length refers to, forexample, a distance, observed in a top view of a transistor, between asource (a source region or a source electrode) and a drain (a drainregion or a drain electrode) in a region where a semiconductor (or aportion where a current flows in a semiconductor when the transistor ison) and a gate electrode overlap with each other or a region where achannel is formed. In one transistor, channel lengths are notnecessarily the same in all regions. In other words, the channel lengthof one transistor is not limited to one value in some cases. Therefore,in this specification, the channel length is any one of values, themaximum value, the minimum value, or the average value in a region wherea channel is formed.

The channel width refers to, for example, the length of a portion wherea source and a drain face each other in a region where a semiconductor(or a portion where a current flows in a semiconductor when a transistoris on) and a gate electrode overlap with each other, or a region where achannel is formed. In one transistor, channel widths are not necessarilythe same in all regions. In other words, the channel width of onetransistor is not limited to one value in some cases. Therefore, in thisspecification, a channel width is any one of values, the maximum value,the minimum value, or the average value in a region where a channel isformed.

Note that depending on transistor structures, a channel width in aregion where a channel is formed actually (hereinafter referred to as aneffective channel width) is different from a channel width shown in atop view of a transistor (hereinafter referred to as an apparent channelwidth) in some cases. For example, in a transistor having a gateelectrode covering a side surface of a semiconductor, an effectivechannel width is greater than an apparent channel width, and itsinfluence cannot be ignored in some cases. For example, in aminiaturized transistor having a gate electrode covering a side surfaceof a semiconductor, the proportion of a channel region formed in a sidesurface of a semiconductor is higher than the proportion of a channelregion formed in a top surface of a semiconductor in some cases. In thatcase, an effective channel width is greater than an apparent channelwidth.

In such a case, an effective channel width is difficult to measure insome cases. For example, to estimate an effective channel width from adesign value, it is necessary to assume that the shape of asemiconductor is known as an assumption condition. Therefore, in thecase where the shape of a semiconductor is not known accurately, it isdifficult to measure an effective channel width accurately.

Therefore, in this specification, an apparent channel width is referredto as a surrounded channel width (SCW) in some cases. Furthermore, inthis specification, in the case where the term “channel width” is simplyused, it may denote a surrounded channel width and an apparent channelwidth. Alternatively, in this specification, in the case where the term“channel width” is simply used, it may denote an effective channel widthin some cases. Note that a channel length, a channel width, an effectivechannel width, an apparent channel width, a surrounded channel width,and the like can be determined by analyzing a cross-sectional TEM imageand the like.

Note that in the case where electric field mobility, a current value perchannel width, and the like of a transistor are calculated, a surroundedchannel width might be used for the calculation. In that case, a valuemight be different from one calculated by using an effective channelwidth.

Embodiment 1

A structure and a manufacturing method of a display device 100 of oneembodiment of the present invention are described with reference toFIGS. 1A to 1C, FIGS. 2A and 2B, FIGS. 3A and 3B, FIGS. 4A to 4E, FIGS.5A to 5C, FIGS. 6A and 6B, FIGS. 7A to 7D, FIGS. 8A to 8D, FIGS. 9A to9D, FIGS. 10A to 10C, FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13Aand 13B, FIGS. 14A and 14B, FIGS. 15A and 15B, FIGS. 16A and 16B, FIGS.17A and 17B, FIGS. 18A and 18B, and FIGS. 19A to 19C. Note that thedisplay device 100 disclosed in this specification is a display devicein which a light-emitting element is used as a display element. As thedisplay device 100 of one embodiment of the present invention, a displaydevice having a top-emission structure is described as an example. Notethat the display device 100 can be a display device having abottom-emission structure or a dual-emission structure.

<Structure of Display Device>

A structure example of the display device 100 of one embodiment of thepresent invention is described with reference to FIGS. 1A to 1C, FIGS.2A and 2B, and FIGS. 3A and 3B. FIG. 1A is a perspective view of thedisplay device 100. FIG. 1B is a cross-sectional view taken along thedashed-dotted line A1-A2 in FIG. 1A. FIG. 1C is a cross-sectional viewtaken along the dashed-dotted line B1-B2 in FIG. 1A. The display device100 described in this embodiment includes a display region 131. Thedisplay region 131 includes a plurality of pixels 130. One pixel 130includes at least one light-emitting element 125.

The display device 100 described in this embodiment includes alight-emitting element 125 including an electrode 115, an EL layer 117,and an electrode 118, a partition 114, and an electrode 116. The displaydevice 100 further includes an insulating layer 141 over the electrode116, and the electrode 115 and the electrode 116 are electricallyconnected to each other in an opening provided in the insulating layer141. The partition 114 is provided over the electrode 115, the EL layer117 is provided over the electrode 115 and the partition 114, and theelectrode 118 is provided over the EL layer 117.

The display device 100 described in this embodiment includes a substrate121 over the light-emitting element 125 with the bonding layer 120positioned therebetween. The substrate 121 includes a touch sensor 271that includes an electrode 272, an insulating layer 273, and anelectrode 274; an electrode 276; an insulating layer 275; alight-blocking layer 264; a coloring layer (also referred to as a colorfilter) 266; and an overcoat layer 268. Between the substrate 121 andthese components, a bonding layer 122 and an insulating layer 129 areprovided. In this embodiment, a capacitive touch sensor is described asan example of the touch sensor 271.

Since the display device 100 described in this embodiment has atop-emission structure, light 151 emitted from the light-emittingelement 125 is extracted from the substrate 121 side. The light 151(e.g., white light) emitted from the EL layer 117 is partly absorbedwhen transmitted through the coloring layer 266 and converted into lightwith a specific color. In other words, the coloring layer 266 transmitslight with a specific wavelength range. The coloring layer 266 canfunction as an optical filter layer for converting the light 151 intolight of a different color.

Although a stacked-layer structure of an electrode 116 a and anelectrode 116 b is described as the electrode 116 in this embodiment,the electrode 116 may have a single-layer structure or a stacked-layerstructure of three or more layers. Although a stacked-layer structure ofan electrode 276 a and an electrode 276 b is described as the electrode276 in this embodiment, the electrode 276 may have a single-layerstructure or a stacked-layer structure of three or more layers.

The display device 100 described in this embodiment includes an opening132 a that penetrates the substrate 121, the bonding layer 122, theinsulating layer 129, the bonding layer 120, the insulating layer 273,the insulating layer 275, and the insulating layer 141 and that overlapswith the electrode 116. The display device 100 further includes anopening 132 b that penetrates the substrate 121, the bonding layer 122,and the insulating layer 129 and that overlaps with the electrode 276.

In the opening 132 a, an external electrode 124 a and the electrode 116are electrically connected to each other through an anisotropicconductive connection layer 138 a. In the opening 132 b, an externalelectrode 124 b and the electrode 276 are electrically connected to eachother through an anisotropic conductive connection layer 138 b.

Note that as illustrated in FIGS. 2A and 2B, it is possible not toprovide the light-blocking layer 264, the coloring layer 266, and theovercoat layer 268 in the display device 100. FIG. 2A is a perspectiveview of the display device 100 in which the light-blocking layer 264,the coloring layer 266, and the overcoat layer 268 are not provided, andFIG. 2B is a cross-sectional view taken along the dashed-dotted lineA1-A2 in FIG. 2A.

In particular, in the case where the EL layer 117 is provided by what iscalled side-by-side patterning in which the colors of the lights 151emitted from different pixels are different, the coloring layer 266 maybe provided or is not necessarily provided.

When at least one or all of the light-blocking layer 264, the coloringlayer 266, and the overcoat layer 268 are not provided, the displaydevice 100 can achieve a reduction in manufacturing cost, yieldimprovement, or the like. Moreover, the light 151 can be emittedefficiently when the coloring layer 266 is not provided; therefore,luminance can be improved or power consumption can be reduced, forexample.

On the other hand, when the light-blocking layer 264, the coloring layer266, and the overcoat layer 268 are provided, reflection of externallight is suppressed and thus a contrast ratio, color reproducibility, orthe like can be improved.

Note that in the case where the display device 100 has a bottom-emissionstructure, the touch sensor 271, the light-blocking layer 264, thecoloring layer 266, and the overcoat layer 268 may be provided on thesubstrate 111 side (see FIG. 3A).

In the case where the display device 100 has a dual-emission structure,the touch sensor 271, the light-blocking layer 264, the coloring layer266, and the overcoat layer 268 may be provided on either or both of thesubstrate 111 side and the substrate 121 side (see FIG. 3B).Alternatively, the touch sensor 271 and the coloring layer 266 may beprovided on the different substrate sides.

A switching element having a function of supplying a signal to thelight-emitting element 125 may be provided between the light-emittingelement 125 and the electrode 116. For example, a transistor may beprovided between the light-emitting element 125 and the electrode 116.

A transistor is a kind of semiconductor element and enablesamplification of current and/or voltage, switching operation forcontrolling conduction or non-conduction, or the like. By providing atransistor between the light-emitting element 125 and the electrode 116,an increase in the area of the display region 131 and ahigher-resolution display can be achieved easily. Note that a resistor,an inductor, a capacitor, a rectifier element, or the like, withoutlimitation to a switching element such as a transistor, can be providedin the display region 131.

[Substrates 111 and 121]

An organic resin material, a glass material that is thin enough to haveflexibility, a metal material that is thin enough to have flexibility(including an alloy material), or the like can be used for the substrate111 and/or the substrate 121. In the case where the display device 100has a bottom-emission structure or a dual-emission structure, a materialhaving a light-transmitting property with respect to light emitted fromthe EL layer 117 is used for the substrate 111. In the case where thedisplay device 100 is a top-emission display device or a dual-emissiondisplay device, a material that transmits light emitted from the ELlayer 117 is used for the substrate 121.

Particularly, the organic resin material has a specific gravity smallerthan that of the glass material or the metal material. Thus, when anorganic resin material is used for the substrate 111 and/or thesubstrate 121, the weight of the display device can be reduced.

The substrate 111 and/or the substrate 121 is/are preferably formedusing a material with high toughness. In that case, a display devicewith high impact resistance that is less likely to be broken can beprovided. The organic resin material and the metal material have highertoughness than the glass material in many cases. When the organic resinmaterial or the metal material is used as the substrate 111 and/or thesubstrate 121, a display device that is less likely to be broken can beprovided as compared with the case of using the glass material.

The metal material has higher thermal conductivity than the organicresin material or the glass material and thus can easily conduct heat tothe whole substrate. Accordingly, a local temperature rise in thedisplay device can be suppressed. The thickness of the substrate 111and/or the substrate 121 using the metal material is preferably greaterthan or equal to 10 μm and less than or equal to 200 μm, or furtherpreferably greater than or equal to 20 μm and less than or equal to 50μm.

Although there is no particular limitation on the metal material usedfor the substrate 111 and/or the substrate 121, for example, aluminum,copper, nickel, an alloy such as an aluminum alloy or stainless steelcan be used.

When a material with high thermal emissivity is used for the substrate111 and/or the substrate 121, the surface temperature of the displaydevice can be prevented from rising, leading to prevention of breakageor a decrease in reliability of the display device. For example, thesubstrate may have a stacked-layer structure of a layer formed using themetal material (hereinafter referred to as a “metal layer”) and a layerwith high thermal emissivity (e.g., a metal oxide or a ceramicmaterial).

A hard coat layer (e.g., a silicon nitride layer) by which a surface ofthe display device is protected from damage, a layer (e.g., an aramidresin layer) which can disperse pressure, or the like may be stackedwith the substrate 111 and/or the substrate 121.

The substrate 111 and/or the substrate 121 may have a stacked-layerstructure of a plurality of layers using the above-described materials.In the case of a structure including a layer formed using a glassmaterial (hereinafter referred to as a “glass layer”), barrierproperties of the display device against water and oxygen can beparticularly improved and thus a reliable display device can beprovided.

For example, a flexible substrate in which a glass layer, a bondinglayer, and a layer formed using the organic resin material (hereinafterreferred to as an “organic resin layer”) are stacked from the sidecloser to the display element can be used. The thickness of the glasslayer is greater than or equal to 20 μm and less than or equal to 200μm, or preferably greater than or equal to 25 μm and less than or equalto 100 μm. With such a thickness, the glass layer can have both a highbarrier property against water and oxygen and a high flexibility. Thethickness of the organic resin layer is greater than or equal to 10 μmand less than or equal to 200 μm, or preferably greater than or equal to20 μm and less than or equal to 50 μm. With such an organic resin layerprovided on an outer side than the glass layer, breakage or a crack ofthe glass layer can be inhibited, resulting in increased mechanicalstrength of the display device. With the substrate using a compositelayer of the glass layer and the organic resin layer, a highly reliableflexible display device can be provided.

As a material that has flexibility and transmits visible light, whichcan be used for the substrate 111 and the substrate 121, the followingcan be used: a poly(ethylene terephthalate) resin (PET), a poly(ethylenenaphthalate) resin (PEN), a poly(ether sulfone) resin (PES), apolyacrylonitrile resin, an acrylic resin, a polyimide resin, apoly(methyl methacrylate) resin, a polycarbonate resin, a polyamideresin, a polycycloolefin resin, a polystyrene resin, a poly(amide imide)resin, a polypropylene resin, a polyester resin, a poly(vinyl halide)resin, an aramid resin, an epoxy resin, or the like. Alternatively, amixture or a stack including any of these materials may be used. Notethat the same material or different materials may be used for thesubstrate 111 and the substrate 121.

The thermal expansion coefficients of the substrate 121 and thesubstrate 111 are preferably less than or equal to 30 ppm/K, or furtherpreferably less than or equal to 10 ppm/K. On surfaces of the substrate121 and the substrate 111, a protective film having low waterpermeability may be formed; examples of the protective film include afilm containing nitrogen and silicon such as a silicon nitride film or asilicon oxynitride film and a film containing nitrogen and aluminum suchas an aluminum nitride film. Note that a structure in which a fibrousbody is impregnated with an organic resin (also called prepreg) may beused as the substrate 121 and the substrate 111.

[Insulating Layers 119, 129, 141, 273, and 275]

The insulating layers 119, 129, 141, 273, and 275 can be formed to havea single-layer structure or a multi-layer structure using an oxidematerial such as aluminum oxide, magnesium oxide, silicon oxide, siliconoxynitride, gallium oxide, germanium oxide, yttrium oxide, zirconiumoxide, lanthanum oxide, neodymium oxide, hafnium oxide, or tantalumoxide; a nitride material such as silicon nitride, silicon nitrideoxide, aluminum nitride, or aluminum nitride oxide; or the like. Theinsulating layer 119 may have, for example, a two-layer structure ofsilicon oxide and silicon nitride or a five-layer structure in whichmaterials selected from the above are combined. The insulating layers119, 129, 141, 273, and 275 can be formed by a sputtering method, a CVDmethod, a thermal oxidation method, a coating method, a printing method,or the like.

The insulating layer 119 can prevent or reduce diffusion of an impurityelement from the substrate 111, the bonding layer 112, or the like tothe light-emitting element 125. The insulating layer 119 is preferablyformed using an insulating film having low water permeability. Forexample, the water vapor permeability is lower than or equal to 1×10⁻⁵g/(m²·day), preferably lower than or equal to 1×10⁻⁶ g/(m²·day), furtherpreferably lower than or equal to 1×10 g/(m²·day), or still furtherpreferably lower than or equal to 1×10⁻⁸ g/(m²·day).

Note that in this specification, a nitride oxide refers to a compoundthat contains more nitrogen than oxygen. An oxynitride refers to acompound that contains more oxygen than nitrogen. The content of eachelement can be measured by Rutherford backscattering spectrometry (RBS),for example.

[Electrodes 116 and 276]

The electrodes 116 a and 276 a can be formed using a conductivematerial. For example, a metal element selected from aluminum, chromium,copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum,tungsten, hafnium (Hf), vanadium (V), niobium (Nb), manganese,magnesium, zirconium, beryllium, and the like; an alloy containing anyof the above metal elements; an alloy containing a combination of theabove metal elements; or the like can be used. A semiconductor typifiedby polycrystalline silicon containing an impurity element such asphosphorus, or silicide such as nickel silicide may also be used. Thereis no particular limitation on the formation method of the electrodes116 a and 276 a, and a variety of formation methods such as anevaporation method, a CVD method, a sputtering method, and a spincoating method can be employed.

The electrodes 116 a and 276 a can also be formed using a conductivematerial containing oxygen, such as indium tin oxide (hereinafter, alsoreferred to as ITO), indium oxide containing tungsten oxide, indium zincoxide containing tungsten oxide, indium oxide containing titanium oxide,indium tin oxide containing titanium oxide, indium zinc oxide, or indiumtin oxide to which silicon oxide is added. Moreover, a conductivematerial containing nitrogen, such as titanium nitride, tantalumnitride, or tungsten nitride, can be used. It is also possible to use astacked-layer structure formed using the above conductive materialcontaining oxygen and a material containing the above metal element.

The electrodes 116 a and 276 a may have a single-layer structure or astacked-layer structure of two or more layers. For example, asingle-layer structure of an aluminum layer containing silicon, atwo-layer structure in which a titanium layer is stacked over analuminum layer, a two-layer structure in which a titanium layer isstacked over a titanium nitride layer, a two-layer structure in which atungsten layer is stacked over a titanium nitride layer, a two-layerstructure in which a tungsten layer is stacked over a tantalum nitridelayer, and a three-layer structure in which a titanium layer, analuminum layer, and a titanium layer are stacked in this order aregiven. Alternatively, an alloy containing one or more elements selectedfrom titanium, tantalum, tungsten, molybdenum, chromium, neodymium, andscandium may be used as the electrode 116 a and the electrode 276 a.

The electrodes 116 b and 276 b can be formed using an element selectedfrom tungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt,zirconium, ruthenium, rhodium, palladium, osmium, iridium, and silicon;an alloy containing any of the elements; or a compound containing any ofthe elements. The electrode 116 b and 276 b can also be formed to have asingle-layer structure or a stacked-layer structure using any of thematerials. Note that the crystalline structure of the electrodes 116 band 276 b may be amorphous, microcrystalline, or polycrystalline. Thepeeling layer 113 can also be formed with a metal oxide such as aluminumoxide, gallium oxide, zinc oxide, titanium dioxide, indium oxide, indiumtin oxide, indium zinc oxide, or an oxide including indium, gallium, andzinc (In—Ga—Zn—O, IGZO).

In the case where each of the electrodes 116 b and 276 b has asingle-layer structure, each of the electrodes 116 b and 276 b ispreferably formed using tungsten, molybdenum, or a material containingtungsten and molybdenum. Alternatively, each of the electrodes 116 b and276 b is preferably formed using an oxide or oxynitride of tungsten, anoxide or oxynitride of molybdenum, or an oxide or oxynitride of amaterial containing tungsten and molybdenum.

[Electrode 115]

The electrode 115 is preferably formed using a conductive material thatefficiently reflects light emitted from the EL layer 117 formed later.Note that the electrode 115 may have a stacked-layer structure of aplurality of layers without limitation to a single-layer structure. Forexample, in the case where the electrode 115 is used as an anode, alayer in contact with the EL layer 117 may be a light-transmittinglayer, such as an indium tin oxide layer, and a layer having highreflectance (e.g., aluminum, an alloy containing aluminum, or silver)may be provided in contact with the layer.

For the conductive material that reflects visible light, for example, ametal material such as aluminum, gold, platinum, silver, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, or palladium or analloy containing any of these metal materials can be used. Lanthanum,neodymium, germanium, or the like may be added to the metal material orthe alloy. In addition, an alloy containing aluminum (an aluminum alloy)such as an alloy of aluminum and titanium, an alloy of aluminum andnickel, or an alloy of aluminum and neodymium; or an alloy containingsilver such as an alloy of silver and copper, an alloy of silver,copper, and palladium, or an alloy of silver and magnesium can be used.An alloy of silver and copper is preferable because of its high heatresistance. Furthermore, a metal film or an alloy film may be stackedwith a metal oxide film. For example, a metal film or an alloy film maybe stacked with an aluminum alloy film, by which oxidation of thealuminum alloy film can be suppressed. Other examples of the metal filmand the metal oxide film are titanium and titanium oxide, respectively.Alternatively, as described above, a light-transmitting conductive filmand a film containing metal materials may be stacked. For example, astack of silver and indium tin oxide, a stack of an alloy of silver andmagnesium and ITO, or the like can be used.

The display device having a top-emission structure is described as anexample in this embodiment. In the case of a display device having abottom-emission structure or a dual emission structure, the electrode115 may be formed using a light-transmitting conductive material.

As a light-transmitting conductive material, indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used, for example. Alternatively, a film of a metalmaterial such as gold, silver, platinum, magnesium, nickel, tungsten,chromium, molybdenum, iron, cobalt, copper, palladium, or titanium; analloy containing any of these metal materials; or a nitride of any ofthese metal materials (e.g., titanium nitride) can be formed thin so asto have a light-transmitting property. Alternatively, a stack of any ofthe above materials can be used as the conductive layer. For example, astack of ITO and an alloy of silver and magnesium is preferably used, inwhich case conductivity can be increased. Further alternatively,graphene or the like may be used.

[Partition 114]

The partition 114 is provided in order to prevent an electrical shortcircuit between the adjacent electrodes 118. In the case of using ametal mask for formation of the EL layer 117 described later, thepartition 114 has a function of preventing the contact of metal maskwith a region where the light-emitting element 125 is formed. Thepartition 114 can be formed of an organic resin material such as anepoxy resin, an acrylic resin, or an imide resin or an inorganicmaterial such as silicon oxide. The partition 114 is preferably formedso that its sidewall has a tapered shape or a tilted surface with acontinuous curvature. The sidewall of the partition 114 having theabove-described shape enables favorable coverage with the EL layer 117and the electrode 118 formed later.

[EL Layer 117]

A structure of the EL layer 117 is described in Embodiment 7.

[Electrode 118]

The electrode 118 is used as a cathode in this embodiment, and thus theelectrode 118 is preferably formed using a material that has a low workfunction and can inject electrons into the EL layer 117 described later.As well as a single-layer of a metal having a low work function, a stackin which a metal material such as aluminum, a conductive oxide materialsuch as indium tin oxide, or a semiconductor material is formed over aseveral-nanometer-thick buffer layer formed of an alkali metal or analkaline earth metal having a low work function may be used as theelectrode 118. As the buffer layer, an oxide of an alkaline earth metal,a halide, a magnesium-silver, or the like can also be used.

In the case where light emitted from the EL layer 117 is extractedthrough the electrode 118, the electrode 118 preferably has a propertyof transmitting visible light.

[Electrodes 272 and 274]

The electrodes 272 and 274 are preferably formed with alight-transmitting conductive material.

[Bonding Layers 120, 112, and 122]

A light curable adhesive, a reaction curable adhesive, a thermosettingadhesive, or an anaerobic adhesive can be used as the bonding layer 120,the bonding layer 112, and the bonding layer 122. For example, an epoxyresin, an acrylic resin, a silicone resin, a phenol resin, an imideresin, a poly(vinyl chloride) (PVC) resin, a poly(vinyl butyral) (PVB)resin, or an ethylene-vinyl acetate (EVA) resin can be used. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferable. Alternatively, an adhesive sheet or the like maybe used.

The bonding layer 120 may contain a drying agent. In particular, in thecase of a display device having a top-emission structure or adual-emission structure, a drying agent (a substance which adsorbsmoisture by chemical adsorption (e.g., oxide of an alkaline earth metalsuch as calcium oxide or barium oxide) or a substance that adsorbsmoisture by physical adsorption, such as zeolite or silica gel) having asize less than or equal to the wavelength of light emitted from the ELlayer 117 or a filler (e.g., titanium oxide or zirconium) with a highrefractive index is preferably mixed into the bonding layer 120, inwhich case the efficiency of extracting light emitted from the EL layer117 negligibly decreases, impurity such as moisture is prevented fromentering a display element, and the reliability of the display device isimproved.

[Anisotropic Conductive Connection Layers 138 a and 138 b]

The anisotropic conductive connection layers 138 a and 138 b can beformed using any of various kinds of anisotropic conductive films (ACF),anisotropic conductive pastes (ACP), and the like.

The anisotropic conductive connection layer 138 is formed by curing apaste-form or sheet-form material that is obtained by mixing conductiveparticles to a thermosetting resin or a thermosetting and light curableresin. The anisotropic conductive connection layer 138 exhibits ananisotropic conductive property by light irradiation orthermocompression bonding. As the conductive particles used for theanisotropic conductive connection layer 138, for example, particles of aspherical organic resin coated with a thin-film metal such as Au, Ni, orCo can be used.

<Method of Manufacturing Display Device>

Next, an example of a method of manufacturing the display device 100 isdescribed with reference to FIGS. 4A to 4E, FIGS. 5A to 5C, FIGS. 6A and6B, FIGS. 7A to 7D, FIGS. 8A to 8D, FIGS. 9A to 9D, FIGS. 10A to 10C,FIGS. 11A and 11B, FIGS. 12A and 12B, FIGS. 13A and 13B, FIGS. 14A and14B, FIGS. 15A and 15B, and FIGS. 16A and 16B. FIGS. 4A to 9D and FIGS.11A to 16B are cross-sectional views taken along the dashed-dotted lineA1-A2 or B1-B2 in FIG. 1A. First, a method of manufacturing an elementsubstrate 171 is described.

[Formation of Peeling Layer 113]

First, a peeling layer 113 is formed over the substrate 101 (see FIG.4A). The substrate 101 may be exemplified by a semiconductor substrate(e.g., a single crystal substrate or a silicon substrate), an SOIsubstrate having heat resistance to the processing temperature in thisembodiment, a glass substrate, a quartz substrate, a sapphire substrate,a ceramic substrate, a plastic substrate, a metal substrate, a stainlesssteel substrate, a substrate including stainless steel foil, a tungstensubstrate, and a substrate including tungsten foil. As an example of aglass substrate, a barium borosilicate glass substrate, analuminoborosilicate glass substrate, and soda lime glass substrate canbe given.

The peeling layer 113 can be formed using an element selected fromtungsten, molybdenum, titanium, tantalum, niobium, nickel, cobalt,zirconium, ruthenium, rhodium, palladium, osmium, iridium, and silicon;an alloy material containing any of the elements; or a compound materialcontaining any of the elements. The peeling layer 113 can also be formedto have a single-layer structure or a stacked-layer structure using anyof the materials. Note that the crystalline structure of the peelinglayer 113 may be amorphous, microcrystalline, or polycrystalline. Thepeeling layer 113 can also be formed using a metal oxide such asaluminum oxide, gallium oxide, zinc oxide, titanium dioxide, indiumoxide, indium tin oxide, indium zinc oxide, or In—Ga—Zn—O (IGZO).

The peeling layer 113 can be formed by a sputtering method, a CVDmethod, a coating method, a printing method, or the like. Note that thecoating method includes a spin coating method, a droplet dischargemethod, and a dispensing method.

In the case where the peeling layer 113 has a single-layer structure,the peeling layer 113 is preferably formed using tungsten, molybdenum,or a material containing tungsten and molybdenum. Alternatively, thepeeling layer 113 is preferably formed using an oxide or oxynitride oftungsten, an oxide or oxynitride of molybdenum, or an oxide oroxynitride of a material containing tungsten and molybdenum.

In the case where the peeling layer 113 has a stacked-layer structureincluding, for example, a layer containing tungsten and a layercontaining an oxide of tungsten, the layer containing an oxide oftungsten may be formed as follows: the layer containing tungsten isformed first and then an insulating oxide layer is formed in contacttherewith, so that the layer containing an oxide of tungsten is formedat the interface between the layer containing tungsten and theinsulating oxide layer. Alternatively, the layer containing an oxide oftungsten may be formed by performing thermal oxidation treatment, oxygenplasma treatment, treatment with an oxidizing solution such as ozonewater, or the like on the surface of the layer containing tungsten.Moreover, an insulating layer may be provided between the substrate 101and the peeling layer 113.

In this embodiment, aluminoborosilicate glass is used for the substrate101. As the peeling layer 113, a tungsten film is formed over thesubstrate 101 by a sputtering method.

[Formation of Insulating Layer 119]

Next, the insulating layer 119 is formed over the peeling layer 113 (seeFIG. 4A). The insulating layer 119 can prevent or reduce diffusion of animpurity element from the substrate 101 or the like. After the substrate101 is replaced with the substrate 111, the insulating layer 119 canprevent or reduce diffusion of an impurity element from the substrate111, the bonding layer 112, or the like to the light-emitting element125. The thickness of the insulating layer 119 is preferably greaterthan or equal to 30 nm and less than or equal to 2 μm, furtherpreferably greater than or equal to 50 nm and less than or equal to 1μm, or still further preferably greater than or equal to 50 nm and lessthan or equal to 500 nm. In this embodiment, the insulating layer 119 isformed by stacking a 600-nm-thick silicon oxynitride film, a200-nm-thick silicon nitride film, a 200-nm-thick silicon oxynitridefilm, a 140-nm-thick silicon nitride oxide film, and a 100-nm-thicksilicon oxynitride film by a plasma CVD method from the substrate 101side.

Note that it is preferable to expose the surface of the peeling layer113 to an atmosphere containing oxygen before the formation of theinsulating layer 119.

As the gas used in the atmosphere containing oxygen, oxygen, dinitrogenmonoxide, nitrogen dioxide, carbon dioxide, carbon monoxide, or the likecan be used. A mixed gas of a gas containing oxygen and another gas maybe used. For example, a mixed gas of a gas containing oxygen and a raregas, for example, a mixed gas of carbon dioxide and argon may be used.Oxidizing the surface of the peeling layer 113 can facilitate peeling ofthe substrate 101 performed later.

[Formation of Electrode 116]

Next, a conductive layer 126 a and a conductive layer 126 b for formingthe electrode 116 are formed over the insulating layer 119. First, asthe conductive layer 126 a, a three-layer metal film in which a layer ofaluminum is provided between two layers of molybdenum is formed over theinsulating layer 119 by a sputtering method. Subsequently, as theconductive layer 126 b, a tungsten film is formed over the conductivelayer 126 a by a sputtering method (see FIG. 4A).

After that, a resist mask is formed over the conductive layer 126 b, andthe conductive layers 126 a and 126 b are etched into a desired shapeusing the resist mask. In the above-described manner, the electrode 116(the electrodes 116 a and 116 b) is formed. The resist mask can beformed by a lithography method, a printing method, an inkjet method, orthe like as appropriate. Formation of the resist mask by an inkjetmethod needs no photomask; thus, manufacturing cost can be reduced.

The etching of the conductive layers 126 a and 126 b may be performed bya dry etching method, a wet etching method, or both of them. After theetching treatment, the resist mask is removed (see FIG. 4B).

When the electrode 116 (including other electrodes and wirings formedusing the same layer) has a taper-shaped end portion, the coverage witha layer that covers the side surfaces of the electrode 116 can beimproved. Specifically, the end portion has a taper angle θ of 80° orless, preferably 60° or less, or further preferably 45° or less. Notethat the “taper angle” refers to an inclination angle formed by a sidesurface and a bottom surface. A taper angle smaller than 90° is calledforward tapered angle and a taper angle larger than or equal to 90° iscalled inverse tapered angle (see FIG. 4B).

Alternatively, the cross-sectional shape of the end portion of theelectrode 116 has a plurality of steps, so that the coverage with thelayer formed thereon can be improved. The above description is notlimited to the electrode 116 and, when the end portion of each layer hasa forward taper shape or a step-like shape in a cross section, aphenomenon that a layer formed to cover the end portion is cut(disconnection) at the end portion can be prevented, so that thecoverage becomes favorable.

[Formation of Insulating Layer 141]

Next, an insulating layer 141 is formed over the electrode 116 (see FIG.4C). In this embodiment, a silicon oxynitride film is formed by a plasmaCVD method as the insulating layer 141. It is preferable to oxidize thesurface of the electrode 116 b prior to the formation of the insulatinglayer 141. For example, it is preferable to expose the surface of theelectrode 116 b to an atmosphere of a gas containing oxygen or anatmosphere of plasma containing oxygen before the formation of theinsulating layer 141. Oxidizing the surface of the electrode 116 b canfacilitate formation of the opening 132 a performed later.

In this embodiment, the sample is placed in a treatment chamber of aplasma CVD apparatus, and then dinitrogen monoxide is supplied to thetreatment chamber and the plasma atmosphere is generated. After that,the sample surface is exposed to the plasma atmosphere. Subsequently, asilicon oxynitride film is formed on the sample surface.

Next, a resist mask is formed over the insulating layer 141, and part ofthe insulating layer 141 overlapping with the electrode 116 isselectively removed using the resist mask, so that the insulating layer141 having an opening 128 is formed (see FIG. 4D). The etching of theinsulating layer 141 may be performed by a dry etching method, a wetetching method, or both of them. At this time, an oxide on the surfaceof the electrode 116 b overlapping with the opening 128 is also removed.

[Formation of Electrode 115]

Next, a conductive layer 145 for forming the electrode 115 is formedover the insulating layer 141 (see FIG. 4E). The conductive layer 145can be formed using a material and a method that are similar to those ofthe conductive layer 126 a (electrode 116 a).

Next, a resist mask is formed over the conductive layer 145, and part ofthe conductive layer 145 is selectively removed using the resist mask,so that the electrode 115 is formed (see FIG. 5A). The etching of theconductive layer 145 may be performed by a dry etching method, a wetetching method, or both of them. In this embodiment, the conductivelayer 145 (electrode 115) is formed using a material in which indium tinoxide is stacked over silver. The electrode 115 and the electrode 116are electrically connected to each other through the opening 128.

[Formation of Partition 114]

Next, the partition 114 is formed (see FIG. 5B). In this embodiment, thepartition 114 is formed in such a manner that a photosensitive organicresin material is applied by a coating method and processed into adesired shape. In this embodiment, the partition 114 is formed using aphotosensitive polyimide resin.

[Formation of EL Layer 117]

Next, the EL layer 117 is formed over the electrode 115 and thepartition 114 (see FIG. 5C).

[Formation of Electrode 118]

Next, the electrode 118 is formed over the EL layer 117. In thisembodiment, an alloy of magnesium and silver is used for the electrode118. The electrode 118 can be formed by an evaporation method, asputtering method, or the like (see FIG. 6A).

In this embodiment, a structure including the substrate 101 and thelight-emitting element 125 provided over the substrate 101 is referredto as the element substrate 171. FIG. 6A is a cross-sectional view ofthe element substrate 171 taken along the dashed-dotted line A1-A2 inFIG. 1A. FIG. 6B is a cross-sectional view of the element substrate 171taken along the dashed-dotted line B1-B2 in FIG. 1A.

Next, a method of forming a counter substrate that includes a colorfilter is described.

[Formation of Peeling Layer 123]

First, a peeling layer 144 is formed over the substrate 102 (see FIG.7A). The substrate 102 can be formed using a material similar to that ofthe substrate 101. Note that the same material or different materialsmay be used for the substrate 101 and the substrate 102. The peelinglayer 144 can be formed with the same material and method as those ofthe peeling layer 113. Moreover, an insulating layer may be providedbetween the substrate 102 and the peeling layer 144. In this embodiment,aluminoborosilicate glass is used for the substrate 102. As the peelinglayer 144, a tungsten film is formed over the substrate 102 by asputtering method.

Subsequently, a resist mask is formed over the peeling layer 144, andpart of the peeling layer 144 is selectively removed using the resistmask, so that a peeling layer 123 having an opening 139 a (notillustrated in FIGS. 7A to 7D) and an opening 139 b is formed. Theresist mask can be formed by a lithography method, a printing method, aninkjet method, or the like as appropriate. Formation of the resist maskby an inkjet method needs no photomask; thus, manufacturing cost can bereduced.

The etching of the peeling layer 144 may be performed by a dry etchingmethod, a wet etching method, or both of them. After the etchingtreatment, the resist mask is removed (see FIG. 7B).

Note that it is preferable to expose the surface of the peeling layer123 to an atmosphere containing oxygen or a plasma atmosphere containingoxygen after the formation of the peeling layer 123. Oxidizing thesurface of the peeling layer 123 can facilitate peeling of the substrate102 performed later.

[Formation of Insulating Layer 129]

Next, the insulating layer 129 is formed over the peeling layer 123 (seeFIG. 7C). The insulating layer 129 can be formed using a material and amethod that are similar to those of the insulating layer 119. In thisembodiment, the insulating layer 129 is formed by stacking a200-nm-thick silicon oxynitride film, a 140-nm-thick silicon nitrideoxide film, and a 100-nm-thick silicon oxynitride film by a plasma CVDmethod from the substrate 102 side.

[Formation of Electrode 276]

Next, conductive layers 286 a and 286 b for forming the electrode 276over the insulating layer 129 are formed. The material and method offorming the conductive layer 126 a can be used for the conductive layer286 a. The material and method of fainting the conductive layer 126 bcan be used for the conductive layer 286 b.

In this embodiment, a tungsten film is formed as the conductive layer286 b over the insulating layer 129 and openings 139 b by a sputteringmethod. Next, three metal films (an aluminum film is sandwiched betweentwo molybdenum films) are formed as the conductive layer 286 a over theconductive layer 286 b by a sputtering method (see FIG. 7C).

After that, a resist mask is formed over the conductive layer 286 a, andthe conductive layers 286 a and 286 b are etched into a desired shapeusing the resist mask. Thus, the electrode 276 (the electrodes 276 a and276 b) can be formed. The resist mask can be formed by a lithographymethod, a printing method, an inkjet method, or the like as appropriate.Formation of the resist mask by an inkjet method needs no photomask;thus, manufacturing cost can be reduced.

The etching of the conductive layers 286 a and 286 b may be performed bya dry etching method, a wet etching method, or both of them. After theetching treatment, the resist mask is removed (see FIG. 7D).

[Formation of Electrode 272]

Next, the electrode 272 that is electrically connected to the electrode276 is formed over the insulating layer 129. The electrode 272 can beformed by forming a light-transmitting conductive layer over theinsulating layer 129 and the electrode 276 and selectively etching partof the conductive layer. The light-transmitting conductive film can beformed with, for example, the above-described light-transmittingconductive material. In this embodiment, indium tin oxide is used forthe electrode 272 (see FIG. 8A).

[Formation of Insulating Layer 273]

Next, the insulating layer 273 is formed over the electrode 272 and theelectrode 276. In this embodiment, a silicon oxynitride film is formedas the insulating layer 273 by a plasma CVD method (see FIG. 8B).

[Formation of Electrode 274]

Then, the electrode 274 is formed over the insulating layer 273. Theelectrode 274 can be formed by forming a light-transmitting conductivelayer over the insulating layer 273 and selectively etching part of theconductive layer. In this embodiment, indium tin oxide is used for theelectrode 274 (see FIG. 8C).

[Formation of Insulating Layer 275]

Next, the insulating layer 275 is formed over the electrode 274. In thisembodiment, a silicon oxynitride film is formed by a plasma CVD methodas the insulating layer 275 (see FIG. 8D). Note that the insulatinglayer 275 is not necessarily formed.

[Formation of Light-Blocking Layer 264]

Next, the light-blocking layer 264 is formed over the insulating layer275 (see FIG. 9A). The light-blocking layer 264 has functions ofblocking light emitted from an adjacent display element and suppressingcolor mixture between adjacent display elements. Moreover, the coloringlayer 266 is provided such that its end portion overlaps with the endportion of the light-blocking layer 264, whereby light leakage can bereduced. The light-blocking layer 264 may have a single-layer structureor a layered structure of two or more layers. Examples of a material forthe light-blocking layer 264 are a metal material including chromium,titanium, nickel, or the like; an oxide material including chromium,titanium, nickel, or the like; and a resin material including a metalmaterial, a pigment, or dye.

The light-blocking layer 264 can be fouled through a photolithographyprocess. In the case where a high molecular material in which carbonblack is dispersed is used for the light-blocking layer 264, thelight-blocking layer 264 can be formed directly on the insulating layer275 by an inkjet method.

[Formation of Coloring Layer 266]

Next, the coloring layer 266 is formed over the insulating layer 275(see FIG. 9B). As described above, the coloring layer is a colored layerthat transmits light in a specific wavelength range. For example, a red(R) color filter for transmitting light in a red wavelength range, agreen (G) color filter for transmitting light in a green wavelengthrange, a blue (B) color filter for transmitting light in a bluewavelength range, or the like can be used. Each coloring layer 266 isformed in a desired position with any of various materials by a printingmethod, an inkjet method, or a photolithography method. At this time,the coloring layer 266 is preferably provided so as to partly overlapwith the light-blocking layer 264 because light leakage can be reduced.Color display can be performed by providing the coloring layers 266 ofdifferent colors in different pixels.

[Formation of Overcoat Layer 268]

Next, the overcoat layer 268 is formed over the light-blocking layer 264and the coloring layer 266 (see FIG. 9C).

As the overcoat layer 268, an organic insulating layer of an acrylicresin, an epoxy resin, polyimide, or the like can be used. With theovercoat layer 268, an impurity or the like contained in the coloringlayer 266 can be prevented from diffusing into the light-emittingelement 125 side, for example. Note that the overcoat layer 268 is notnecessarily formed.

A light-transmitting conductive film may be formed as the overcoat layer268. The light-transmitting conductive film is formed as the overcoatlayer 268, the overcoat layer 268 can transmit light 151 emitted fromthe light-emitting element 125 and prevent transmission of ionizedimpurities.

The light-transmitting conductive film can be formed with, for example,the above-described light-transmitting conductive material. A metal filmthat is thin enough to have a light-transmitting property can also beused.

In this embodiment, a structure including the substrate 102 and thecoloring layer 266 and the like provided over the substrate 102 isreferred to as a counter substrate 181. Through the above steps, thecounter substrate 181 can be formed. Note that the counter substrate 181is not provided with the coloring layer 266 or the like in some caseswhen the coloring layer 266 is not needed. FIG. 9C is a cross-sectionalview of the counter substrate 181 taken along the dashed-dotted lineB1-B2 in FIG. 1A. FIG. 9D is a cross-sectional view of the countersubstrate 181 taken along the dashed-dotted line A1-A2 in FIG. 1A.

[Example of Pixel Configuration]

Here, examples of a pixel configuration for achieving color display aredescribed with reference to FIGS. 10A to 10C. FIGS. 10A to 10C areenlarged plan views of a region 170 in the display region 131 of FIG.1A.

As illustrated in FIG. 10A, for example, each pixel 130 may function asa subpixel and three pixels 130 may be collectively used as one pixel140. The use of a red, a green, and a blue coloring layers as thecoloring layers 266 for the three pixels 130 enables full-color display.In FIG. 10A, the pixel 130 emitting red light, the pixel 130 emittinggreen light, and the pixel 130 emitting blue light are illustrated as apixel 130R, a pixel 130G, and a pixel 130B, respectively. The colors ofthe coloring layers 266 may be a color other than red, green, and blue;for example, the colors of the coloring layer 266 may be yellow, cyan,magenta, or the like.

As illustrated in FIG. 10B, each pixel 130 may function as a subpixeland four pixels 130 may be collectively used as one pixel 140. Forexample, the coloring layers 266 corresponding to the four pixels 130may be red, green, blue, and yellow. In FIG. 10B, the pixel 130 emittingred light, the pixel 130 emitting green light, the pixel 130 emittingblue light, and the pixel 130 emitting yellow light are illustrated as apixel 130R, a pixel 130G, a pixel 130B, and a pixel 130Y, respectively.By increasing the number of subpixels (pixels 130) included in one pixel140, the color reproducibility can be particularly improved. Thus, thedisplay quality of the display device can be improved. With the pixel130 emitting yellow light (pixel 130Y), the luminance of the displayregion can be increased. Accordingly, power consumption of the displaydevice can be reduced.

Alternatively, the coloring layers 266 corresponding to the four pixels130 may be red, green, blue, and white (see FIG. 10B). With the pixel130 emitting white light (pixel 130W), the luminance of the displayregion can be increased. Accordingly, power consumption of the displaydevice can be reduced.

Note that in the case where the pixel 130 emitting white light isprovided, it is not necessary to provide the coloring layer 266 for thepixel 130W Without a white coloring layer 266, there is no luminancereduction at the time of transmitting light through the coloring layer266; thus, the luminance of the display region can be increased.Moreover, power consumption of the display device can be reduced. On theother hand, color temperature of white light can be changed with thewhite coloring layer 266. Thus, the display quality of the displaydevice can be improved. Depending on the intended use of the displaydevice, each pixel 130 may function as a subpixel and two pixels 130 maybe collectively used as one pixel 140.

Note that the occupation areas or shapes of the pixels 130 may be thesame or different. In addition, arrangement is not limited to stripearrangement. For example, delta arrangement, Bayer arrangement, pentilearrangement, or the like can be used. FIG. 10C illustrates an example ofpentile arrangement.

[Attachment of Element Substrate 171 and Counter Substrate 181]

Next, the element substrate 171 and the counter substrate 181 areattached to each other with the bonding layer 120 positionedtherebetween. At the attachment, the light-emitting element 125 on theelement substrate 171 and the coloring layer 266 on the countersubstrate 181 are disposed to face each other. FIG. 11A is across-sectional view taken along the dashed-dotted line A1-A2 in FIG.1A. FIG. 11B is a cross-sectional view taken along the dashed-dottedline B1-B2 in FIG. 1A.

[Peeling of Substrate 101]

Next, the substrate 101 included in the element substrate 171 is peeledoff from the insulating layer 119 together with the peeling layer 113(see FIGS. 12A and 12B). As a peeling method, mechanical force (apeeling process with a human hand or a gripper, a separation process byrotation of a roller, ultrasonic waves, or the like) may be used. Forexample, a cut is made in the interface between the peeling layer 113and the insulating layer 119 from the side surface of the elementsubstrate 171 with a sharp edged tool, by laser beam irradiation, or thelike, and water is injected into the cut. The interface between thepeeling layer 113 and the insulating layer 119 absorbs water bycapillarity action, so that the substrate 101 can be peeled off easilyfrom the insulating layer 119 together with the peeling layer 113.

[Attachment of Substrate 111]

Next, the substrate 111 is attached to the insulating layer 119 with thebonding layer 112 provided therebetween (see FIGS. 13A and 13B).

[Peeling of Substrate 102]

Next, the substrate 102 included in the counter substrate 181 is peeledoff from the insulating layer 129 together with the peeling layer 123.

Note that before the substrate 102 is peeled off, at least part of theelectrode 116 may be irradiated with light 220 through the opening 139 aas illustrated in FIG. 14A. At least part of the electrode 276 may beirradiated with the light 220 through the opening 139 b as illustratedin FIG. 14B. As the light 220, infrared light, visible light, orultraviolet light emitted from a halogen lamp, a high pressure mercurylamp, or the like can be used. In addition, as the light 220, intenselight such as a continuous wave laser beam or a pulsed laser beam can beused. In particular, the pulsed laser beam is preferable because pulsedlaser beam with high energy can be emitted instantaneously. Thewavelength of the light 220 is preferably 400 nm to 1.2 μm, furtherpreferably 500 nm to 900 nm, or still further preferably 500 nm to 700nm. In the case of the pulsed laser beam used as the light 220, thepulse width is preferably 1 ns (nanosecond) to 1 μs (microsecond),further preferably 5 ns to 500 ns, or still further preferably 5 ns to100 ns. For example, a pulsed laser beam with the wavelength of 532 nmand the pulse width of 10 ns may be used.

By irradiation with the light 220, the temperature of the electrodes 116and 276 rises, and adhesion between the electrode 116 and the insulatinglayer 141 is lowered because of thermal stress, emission of gas thatremains in the layer, or the like. In addition, adhesion between theelectrode 276 and the insulating layer 129 is lowered. As a result, theinsulating layer 141 is easily peeled off from the electrode 116, andthe insulating layer 129 is easily peeled off from the electrode 276.

FIGS. 15A and 15B illustrate a state in which the substrate 102 includedin the counter substrate 181, together with the peeling layer 123, ispeeled off from the insulating layer 129. At this time, part of theinsulating layer 129, part of the insulating layer 273, part of theinsulating layer 275, part of the bonding layer 120, and part of theinsulating layer 141, which are regions overlapping with the opening 139a, are removed to form an opening 132 a 1. The opening 132 a 1 ispreferably formed inside the electrode 116 in the plan view. In otherwords, opening 132 a 1 is preferably formed on the inner side than theend portions of the electrode 116 in the cross-sectional view. That is,the width W1 of the opening 132 a 1 is preferably smaller than the widthW2 of the surface of the electrode 116 (see FIG. 15A).

Part of the insulating layer 129, which is a region overlapping with theopening 139 b, is also removed to form an opening 132 b 1. The opening132 b 1 is preferably formed inside the electrode 276 in the plan view.In other words, opening 132 b 1 is preferably formed on the inner sidethan the end portions of the electrode 276 in the cross-sectional view.That is, the width W1 of the opening 132 b 1 is preferably smaller thanthe width W2 of the surface of the electrode 276 (see FIG. 15B).

At the step of peeling the substrate 102 together with the peeling layer123, the opening 132 a 1 and the opening 132 b 1 can be fruited at thesame time. In one embodiment of the present invention, the steps ofmanufacturing the display device can be reduced, which increases theproductivity of the display device.

[Attachment of Substrate 121]

Next, the substrate 121 having an opening 132 a 2 and an opening 132 b 2is attached to the insulating layer 129 with the bonding layer 122provided therebetween (see FIGS. 16A and 16B). The substrate 121 and theinsulating layer 129 are attached to each other so that the opening 132a 1 overlaps with the opening 132 a 2 and the opening 132 b 1 overlapswith the opening 132 b 2. In this embodiment, the openings 132 a 1 and132 a 2 are collectively referred to as an opening 132 a, and theopenings 132 b 1 and opening 132 b 2 are collectively referred to as anopening 132 b. The surface of the electrode 116 is exposed from theopening 132 a. The surface of the electrode 276 is exposed from theopening 132 b.

In the display device 100 of one embodiment of the present invention,the opening 132 a may overlap with one or more electrodes 116, and theopening 132 b may overlap with one or more electrodes 276. FIG. 17A is aperspective view of the display device 100 that includes two or moreelectrodes 116 that overlaps with the opening 132 a and two or moreelectrodes 276 that overlaps with the opening 132 b. Note that FIG. 17Bis a cross-sectional view taken along the dashed-dotted line C1-C2 inFIG. 17A.

The display device 100 of one embodiment of the present invention mayinclude the opening 132 a with respect to each of the electrodes 116,and the opening 132 b with respect to each of the electrodes 276. Thatis, the display device 100 of one embodiment of the present inventionmay include two or more openings 132 a and two or more openings 132 b.FIG. 18A is a perspective view of the display device 100 in which theopening 132 a overlapping with the electrode 116 is provided in eachelectrode 116, and the opening 132 b overlapping with the electrode 276is provided in each electrode 276. Note that FIG. 18B is across-sectional view taken along the dashed-dotted line C1-C2 in FIG.18A.

Alternatively, the display device 100 of one embodiment of the presentinvention may have a structure in which an opening 132 that overlapswith the electrodes 116 and the electrodes 276 is provided. FIG. 19A isa perspective view of the display device 100 in which the opening 132that overlaps with the electrodes 116 and the electrodes 276 isprovided. FIG. 19B is a cross-sectional view taken along thedashed-dotted line C1-C2 in FIG. 19A. FIG. 19C is a perspective viewillustrating a state in which the external electrode 124 is electricallyconnected to the electrodes 116 and the electrodes 276 through theopening 132. Note that the external electrode 124 may be electricallyconnected to the electrode 116 and the electrode 276 through ananisotropic conductive layer.

The openings 132 a and 132 b are provided on the inner side than the endportion of the substrate 121 in a plan view, so that regions near theopenings 132 a and 132 b can be supported by the substrate 111 and thesubstrate 121. Thus, the mechanical strength of a region where theexternal electrode 124 and the electrode 116 are connected to each otheris unlikely to decrease, and unintentional deformation of the connectedregion can be reduced. Furthermore, since a wiring or the like near theopening 132 a and/or the opening 132 b is sandwiched by the substrate111 and the substrate 121, the wiring or the like is unlikely to beaffected by external shock or external deformation. Accordingly, damageto the wiring or the like can be prevented. Note that an effect ofreducing the deformation of the connected region can be improved in thecase where the opening 132 a is provided for each electrode 116 ascompared with the case where a plurality of electrodes 116 are providedin one opening 132 a. According to one embodiment of the presentinvention, breakage of the display device 100 can be prevented, and thereliability of the display device 100 can be improved.

Moreover, in one embodiment of the present invention, part of theflexible substrate does not need to be removed by a laser beam or withan edged tool to expose the surfaces of the electrodes 116 and 276;thus, the electrodes 116 and 276, the display region 131 and the likeare not damaged easily.

In addition, the opening 132 a and the opening 132 b can be formed atthe same time, which increases the productivity of the display device.

Alternatively, one or more of layers each formed using a material havinga specific function, such as an anti-reflection layer, a light diffusionlayer, a microlens array, a prism sheet, a retardation plate, or apolarizing plate, (hereinafter referred to as “functional layers”) maybe provided on an outer side than the substrate 111 or the substrate 121from which the light 151 is emitted. As the anti-reflection layer, forexample, a circularly polarizing plate or the like can be used. With thefunctional layer, a display device having a higher display quality canbe achieved. Moreover, power consumption of the display device can bereduced.

For the substrate 111 or the substrate 121, a material having a specificfunction may be used. For example, a circularly polarizing plate may beused as the substrate 111 or the substrate 121. Alternatively, forexample, the substrate 111 or the substrate 121 may be formed using aretardation plate, and a polarizing plate may be provided so as tooverlap with the substrate. As another example, the substrate 111 or thesubstrate 121 may be formed using a prism sheet, and a circularlypolarizing plate may be provided so as to overlap with the substrate.With the use of the material having a specific function for thesubstrate 111 or the substrate 121, improvement of display quality andreduction of the manufacturing cost can be achieved.

[Formation of External Electrode]

Next, the anisotropic conductive connection layer 138 a is formed in theopening 132 a, and the external electrode 124 a for inputting electricpower or a signal to the display device 100 is formed over theanisotropic conductive connection layer 138 a. Then, the anisotropicconductive connection layer 138 b is formed in the opening 132 b, andthe external electrode 124 b for inputting electric power or a signal tothe display device 100 is formed over the anisotropic conductiveconnection layer 138 b (see FIGS. 1A to 1C). By electrical connectionbetween the external electrode 124 a and the terminal electrode 116through the anisotropic conductive connection layer 138 a, electricpower or a signal can be input to the display device 100. By electricalconnection between the external electrode 124 b and the terminalelectrode 276 through the anisotropic conductive connection layer 138 b,electric power or a signal can be input to the display device 100.

In one embodiment of the present invention, the electrode 116 and theelectrode 276 can be exposed on the same surface side of the displaydevice 100 (in this embodiment, on the substrate 121 side). This enableseasy connections between the external electrode 124 a and the electrode116 and between the external electrode 124 b and the electrode 276. Forexample, the connections can be performed at the same step. Thus, themanufacturing yield of the display device can be increased. Furthermore,the steps of manufacturing the display device can be reduced, whichincreases the productivity of the display device.

Note that FPCs can be used as the external electrodes 124 a and 124 b.Alternatively, a metal wire can be used as the external electrodes 124 aand 124 b. Although the anisotropic conductive connection layer may beused to connect the metal wire and the electrode 116 or the electrode276, the connection can be made by a wire bonding method. Alternatively,the metal wire and the electrode 116 or the electrode 276 can beconnected by a soldering method.

In one embodiment of the present invention, external electrodes such asthe external electrode 124 a and the external electrode 124 b can beprovided on one surface of the display device 100, whereby the designflexibility of the display device can be increased. Furthermore, thedesign flexibility of a semiconductor device including the displaydevice 100 of one embodiment of the present invention can be increased.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 2

In this embodiment, a display device 1100 having a structure differentfrom the structure of the display device 100 described in the aboveembodiment is described. In this embodiment, a description is made ofportions different from the display device 100 to avoid repetition ofthe same description.

The display device 1100 described in this embodiment is different fromthe display device 100 in connection portions of the external electrodes124 (the external electrode 124 a, external electrode 124 b).Specifically, in the display device 100, the external electrode 124 isconnected from the substrate 121 side, while in the display device 1100,the external electrode 124 is connected from the substrate 111 side. Inaddition, the stacking order of the electrode 116 a and the electrode116 b in the display device 1100 is different from that in the displaydevice 100. The stacking order of the electrode 276 a and the electrode276 b in the display device 1100 is different from that in the displaydevice 100.

<Structure of Display Device>

A structure example of the display device 1100 of one embodiment of thepresent invention is described with reference to FIGS. 20A to 20C, FIGS.21A and 21B, FIGS. 22A and 22B, and FIGS. 23A to 23C. FIG. 20A is aperspective view of the display device 1100. FIG. 20B is across-sectional view taken along the dashed-dotted line A1-A2 in FIG.20A. FIG. 20C is a cross-sectional view taken along the dashed-dottedline B1-B2 in FIG. 20A.

The display device 1100 described in this embodiment includes theopening 132 a that penetrates the substrate 111, the bonding layer 112,and the insulating layer 119 and overlaps with the electrode 116. Thedisplay device 1100 further includes an opening 132 b that penetratesthe substrate 111, the bonding layer 112, the insulating layer 119, theinsulating layer 141, the bonding layer 120, the insulating layer 275,and the insulating layer 273 and that overlaps with the electrode 276.

In the opening 132 a, an external electrode 124 a and the electrode 116are electrically connected to each other through an anisotropicconductive connection layer 138 a. In the opening 132 b, an externalelectrode 124 b and the electrode 276 are electrically connected to eachother through an anisotropic conductive connection layer 138 b.

As in the display device 100, a switching element having a function ofsupplying a signal to the light-emitting element 125 may be providedbetween the light-emitting element 125 and the electrode 116. Forexample, a transistor may be provided between the light-emitting element125 and the electrode 116.

As in the display device 100, in the display device 1100 of oneembodiment of the present invention, the opening 132 a may overlap withone or more electrodes 116, and the opening 132 b may overlap with oneor more electrodes 276. FIG. 21A is a perspective view of the displaydevice 1100 that includes two or more electrodes 116 that overlaps withthe opening 132 a and two or more electrodes 276 that overlaps with theopening 132 b. Note that FIG. 21B is a cross-sectional view taken alongthe dashed-dotted line C1-C2 in FIG. 21A.

Like the display device 100, the display device 1100 of one embodimentof the present invention may include the opening 132 a with respect toeach of the electrodes 116, and the opening 132 b with respect to eachof the electrodes 276. That is, the display device 1100 of oneembodiment of the present invention may include two or more openings 132a and two or more openings 132 b. FIG. 22A is a perspective view of thedisplay device 1100 in which the opening 132 a overlapping with theelectrode 116 is provided in each electrode 116, and the opening 132 boverlapping with the electrode 276 is provided in each electrode 276.Note that FIG. 22B is a cross-sectional view taken along thedashed-dotted line C1-C2 in FIG. 22A.

Like the display device 100, the display device 1100 of one embodimentof the present invention may have a structure in which an opening 132that overlaps with the electrodes 116 and the electrodes 276 isprovided. FIG. 23A is a perspective view of the display device 1100 inwhich the opening 132 that overlaps with the electrodes 116 and theelectrodes 276 is provided. FIG. 23B is a cross-sectional view takenalong the dashed-dotted line C1-C2 in FIG. 23A. FIG. 23C is aperspective view illustrating a state in which the external electrode124 is electrically connected to the electrodes 116 and the electrodes276 through the opening 132. Note that the external electrode 124 may beelectrically connected to the electrode 116 and the electrode 276through an anisotropic conductive layer.

<Method of Manufacturing Display Device>

Next, an example of a method of manufacturing the display device 1100 isdescribed with reference to FIGS. 24A to 24D, FIGS. 25A to 25D, FIGS.26A to 26D, and FIGS. 27A and 27B. FIGS. 24A to 27B are cross-sectionalviews taken along the dashed-dotted line A1-A2 or B1-B2 in FIGS. 20A to20C. First, a method of manufacturing an element substrate 1171 isdescribed.

[Formation of Peeling Layer 113]

First, a peeling layer 154 is formed over the substrate 101 (see FIG.24A). The peeling layer 154 can be formed with the same material andmethod as those of the peeling layer 113. Moreover, an insulating layermay be provided between the substrate 101 and the peeling layer 154.

Next, a resist mask is formed over the peeling layer 154, and part ofthe peeling layer 154 is selectively removed using the resist mask,whereby the peeling layer 113 having the opening 139 a and the opening139 b (not illustrated in FIGS. 24A to 24D) is found. The resist maskcan be formed by a lithography method, a printing method, an inkjetmethod, or the like as appropriate. Formation of the resist mask by aninkjet method needs no photomask; thus, manufacturing cost can bereduced.

The etching of the peeling layer 154 may be performed by a dry etchingmethod, a wet etching method, or both of them. After the etchingtreatment, the resist mask is removed (see FIG. 24B).

Note that it is preferable to expose the surface of the peeling layer113 to an atmosphere containing oxygen or a plasma atmosphere containingoxygen after the formation of the peeling layer 113. Oxidizing thesurface of the peeling layer 113 can facilitate peeling of the substrate101 performed later.

[Formation of Insulating Layer 119]

Next, the insulating layer 119 is formed over the peeling layer 113 (seeFIG. 24C).

[Formation of Electrode 116]

Next, conductive layers 126 b and 126 a for forming the electrode 116are formed over the insulating layer 119. First, a tungsten film isformed as the conductive layer 126 b over the insulating layer 119 by asputtering method. Next, three metal films (an aluminum film issandwiched between two molybdenum films) are formed as the conductivelayer 126 a over the conductive layer 126 b by a sputtering method (seeFIG. 24C).

After that, a resist mask is formed over the conductive layer 126 a, andthe conductive layers 126 b and 126 a are etched into a desired shapeusing the resist mask. Thus, the electrode 116 (the electrodes 116 b and116 a) can be formed (see FIG. 24D). The resist mask can be formed by alithography method, a printing method, an inkjet method, or the like asappropriate. Formation of the resist mask by an inkjet method needs nophotomask; thus, manufacturing cost can be reduced.

[Formation of Insulating Layer 141]

Next, the insulating layer 141 is formed over the electrode 116 (seeFIG. 25A). Then, a resist mask is formed over the insulating layer 141,and part of the insulating layer 141 that overlaps with the electrode116 is selectively removed using the resist mask, whereby the insulatinglayer 141 having the opening 128 is formed (see FIG. 25B).

The following steps can be performed in a manner similar to those of theelement substrate 171 described in the above embodiment. Thus, theelement substrate 1171 can be formed. FIG. 25C is a cross-sectional viewof the element substrate 1171 taken along the dashed-dotted line A1-A2in FIG. 20A. FIG. 25D is a cross-sectional view of the element substrate1171 taken along the dashed-dotted line B1-B2 in FIG. 20A.

Next, a method of forming a counter substrate 1181 is described.

[Formation of Peeling Layer 144]

First, the peeling layer 144 is formed over the substrate 102 (see FIG.26A). The peeling layer 144 can be formed with the same material andmethod as those of the peeling layer 113. Moreover, an insulating layermay be provided between the substrate 102 and the peeling layer 144.

Note that it is preferable to expose the surface of the peeling layer144 to an atmosphere containing oxygen or a plasma atmosphere containingoxygen after the formation of the peeling layer 144. Oxidizing thesurface of the peeling layer 144 can facilitate peeling of the substrate102 performed later.

[Formation of Insulating Layer 129]

Next, the insulating layer 129 is formed over the peeling layer 144 (seeFIG. 26A).

[Formation of Electrode 276]

Next, conductive layers 286 a and 286 b for forming the electrode 276over the insulating layer 129 are formed. First, as the conductive layer286 a, a three-layer metal film in which an aluminum layer is providedbetween two molybdenum layers is formed over the insulating layer 129 bya sputtering method. Next, as the conductive layer 286 b, a tungstenfilm is formed over the conductive layer 286 a by a sputtering method(see FIG. 26A).

After that, a resist mask is formed over the conductive layer 286 b, andthe conductive layers 286 a and 286 b are etched into a desired shapeusing the resist mask. Thus, the electrode 276 (the electrodes 276 a and276 b) can be formed. The resist mask can be formed by a lithographymethod, a printing method, an inkjet method, or the like as appropriate.Formation of the resist mask by an inkjet method needs no photomask;thus, manufacturing cost can be reduced (see FIG. 26B).

[Formation of Electrode 272]

Next, the electrode 272 that is electrically connected to the electrode276 is formed over the insulating layer 129. The electrode 272 can beformed by forming a light-transmitting conductive layer over theinsulating layer 129 and the electrode 276 and selectively etching partof the conductive layer (see FIG. 26C).

[Formation of Insulating Layer 273]

Next, the insulating layer 273 is formed over the electrode 272 and theelectrode 276 (see FIG. 26D).

The following steps can be performed in a manner similar to those of thecounter substrate 181 described in the above embodiment. Thus, thecounter substrate 1181 can be formed. FIG. 27A is a cross-sectional viewof the counter substrate 1181 taken along the dashed-dotted line B1-B2in FIG. 20A. FIG. 27B is a cross-sectional view of the counter substrate1181 taken along the dashed-dotted line A1-A2 in FIG. 20A.

[Attachment of Element Substrate 1171 and Counter Substrate 1181]

Next, the element substrate 1171 and the counter substrate 1181 areattached to each other with the bonding layer 120 positionedtherebetween. At the attachment, the light-emitting element 125 on theelement substrate 1171 and the coloring layer 266 on the countersubstrate 1181 are disposed to face each other. FIG. 28A is across-sectional view taken along the dashed-dotted line A1-A2 in FIG.20A. FIG. 28B is a cross-sectional view taken along the dashed-dottedline B1-B2 in FIG. 20A.

[Peeling of Substrate 102]

Next, the substrate 102 is peeled off from the insulating layer 129together with the peeling layer 123 (see FIGS. 29A and 29B). As apeeling method, mechanical force (a peeling process with a human hand ora gripper, a separation process by rotation of a roller, ultrasonicwaves, or the like) may be used. For example, a cut is made in theinterface between the peeling layer 123 and the insulating layer 129with a sharp edged tool, by laser beam irradiation, or the like, andwater is injected into the cut. The interface between the peeling layer123 and the insulating layer 129 absorbs water by capillarity action, sothat the substrate 102 can be peeled off easily from the insulatinglayer 129 together with the peeling layer 123.

[Attachment of Substrate 121]

Next, the substrate 121 is attached to the insulating layer 129 with thebonding layer 122 provided therebetween (see FIGS. 30A and 30B).

[Peeling of Substrate 101]

Next, the substrate 101 is peeled off from the insulating layer 119together with the peeling layer 113.

Note that before the substrate 101 is peeled off, at least part of theelectrode 116 may be irradiated with light 220 through the opening 139 aas illustrated in FIG. 31A. At least part of the electrode 276 may beirradiated with the light 220 through the opening 139 b as illustratedin FIG. 31B.

FIGS. 32A and 32B illustrate a state in which the substrate 101,together with the peeling layer 113, is peeled off from the insulatinglayer 119. At this time, part of the insulating layer 119, which is aregion overlapping with the opening 139 a, is removed to form theopening 132 a 1 (see FIG. 32A). The opening 132 a 1 is preferably formedinside the electrode 116 in the plan view. In other words, opening 132 a1 is preferably formed on the inner side than the end portions of theelectrode 116 in the cross-sectional view. That is, the width W1 of theopening 132 a 1 is preferably smaller than the width W2 of the surfaceof the electrode 116.

Regions overlapping with the opening 139 b in the insulating layer 119,the insulating layer 141, the bonding layer 120, the insulating layer275, and the insulating layer 273 are removed to form the opening 132 b1 (see FIG. 32B). The opening 132 b 1 is preferably formed inside theelectrode 276 in the plan view. In other words, opening 132 b 1 ispreferably formed on the inner side than the end portions of theelectrode 276 in the cross-sectional view. That is, the width W1 of theopening 132 b 1 is preferably smaller than the width W2 of the surfaceof the electrode 276.

At the step of peeling the substrate 101 together with the peeling layer113, the opening 132 a 1 and the opening 132 b 1 can be formed at thesame time. In one embodiment of the present invention, the steps ofmanufacturing the display device can be reduced, which increases theproductivity of the display device.

[Attachment of Substrate 111]

Next, the substrate 111 having an opening 132 a 2 and an opening 132 b 2is attached to the insulating layer 119 with the bonding layer 112provided therebetween (see FIGS. 33A and 33B). The substrate 111 and theinsulating layer 119 are attached to each other so that the opening 132a 1 overlaps with the opening 132 a 2 and the opening 132 b 1 overlapswith the opening 132 b 2. In this embodiment, the openings 132 a 1 and132 a 2 are collectively referred to as an opening 132 a, and theopenings 132 b 1 and opening 132 b 2 are collectively referred to as anopening 132 b. The surface of the electrode 116 is exposed from theopening 132 a. The surface of the electrode 276 is exposed from theopening 132 b. Thus, the display device 1100 can be manufactured (seeFIGS. 34A and 34B).

In one embodiment of the present invention, part of the flexiblesubstrate does not need to be removed by a laser beam or with an edgedtool to expose the surfaces of the electrodes 116 and 276; thus, theelectrodes 116 and 276, the display region 131 and the like are notdamaged easily.

In addition, the opening 132 a and the opening 132 b can be formed atthe same time, which increases the productivity of the display device.

[Formation of External Electrode]

Next, the anisotropic conductive connection layer 138 a is formed in theopening 132 a, and the external electrode 124 a for inputting electricpower or a signal to the display device 1100 is formed over theanisotropic conductive connection layer 138 a. Then, the anisotropicconductive connection layer 138 b is formed in the opening 132 b, andthe external electrode 124 b for inputting electric power or a signal tothe display device 1100 is formed over the anisotropic conductiveconnection layer 138 b (see FIGS. 20A to 20C). By electrical connectionbetween the external electrode 124 a and the terminal electrode 116through the anisotropic conductive connection layer 138 a, electricpower or a signal can be input to the display device 1100. By electricalconnection between the external electrode 124 b and the terminalelectrode 276 through the anisotropic conductive connection layer 138 b,electric power or a signal can be input to the display device 1100.

In one embodiment of the present invention, external electrodes such asthe external electrode 124 a and the external electrode 124 b can beprovided on one surface of the display device 1100, whereby the designflexibility of the display device can be increased. Furthermore, thedesign flexibility of a semiconductor device including the displaydevice 1100 of one embodiment of the present invention can be increased.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 3

In this embodiment, display devices 200 and 1200 each having a structuredifferent from the structures of the display devices 100 and 1100described in the above embodiments are described with reference to FIGS.35A and 35B and FIGS. 36A and 36B. FIG. 35A is a top view of the displaydevice 200, and FIG. 35B is a cross-sectional view taken along thedashed-dotted line A3-A4 in FIG. 35A. FIG. 36A is a top view of thedisplay device 1200, and FIG. 36B is a cross-sectional view taken alongthe dashed-dotted line A3-A4 in FIG. 36A.

<Structure of Display Device>

The display device 200 and the display device 1200 described in thisembodiment each include a display region 231 and a peripheral circuit251. Each of the display device 200 and the display device 1200 furtherincludes the electrode 116 and the light-emitting element 125 includingthe electrode 115, the EL layer 117, and the electrode 118. A pluralityof light-emitting elements 125 are formed in the display region 231. Atransistor 232 for controlling the amount of light emitted from thelight-emitting element 125 is connected to each light-emitting element125. In the display device 200, the external electrode 124 a isconnected from the substrate 121 side. In the display device 1200, theexternal electrode 124 a is connected from the substrate 111 side.

The electrode 116 is electrically connected to the external electrode124 a through the anisotropic conductive connection layer 138 a formedin the opening 132 a. In addition, the electrode 116 is electricallyconnected to the peripheral circuit 251. Although FIGS. 35A and 35B andFIGS. 36A and 36B illustrate the electrode 116 with a stacked-layerstructure of the electrodes 116 a and 116 b, the electrode 116 may havea single-layer structure or a stacked-layer structure of three or morelayers. The display device 200 in FIGS. 35A and 35B differs from thedisplay device 1200 in FIGS. 36A and 36B in the stacking order of theelectrode 116 a and the electrode 116 b.

The peripheral circuit 251 includes a plurality of transistors 252. Theperipheral circuit 251 has a function of determining which of thelight-emitting elements 125 in the display region 231 is supplied with asignal from the external electrode 124.

In each of the display devices 200 and 1200, the substrate 111 and thesubstrate 121 are attached to each other with the bonding layer 120provided therebetween. An insulating layer 205 is formed over thesubstrate 111 with the bonding layer 112 provided therebetween. Theinsulating layer 205 is preferably formed as a single layer or amultilayer using any of silicon oxide, silicon nitride, siliconoxynitride, silicon nitride oxide, aluminum oxide, aluminum oxynitride,and aluminum nitride oxide. The insulating layer 205 can be formed by asputtering method, a CVD method, a thermal oxidation method, a coatingmethod, a printing method, or the like.

The insulating layer 205 functions as a base layer and can prevent orreduce diffusion of impurity elements from the substrate 111, thebonding layer 112, or the like to the transistor or the light-emittingelement.

The transistor 232, the transistor 252, the electrode 116, and a wiring219 are formed over the insulating layer 205. Although a channel-etchedtransistor that is a type of bottom-gate transistor is illustrated asthe transistor 232 and/or the transistor 252 in this embodiment, achannel-protective transistor, a top-gate transistor, or the like canalso be used. Alternatively, an inverted staggered transistor or aforward staggered transistor can also be used. It is also possible touse a dual-gate transistor, in which a semiconductor layer in which achannel is formed is provided between two gate electrodes. Furthermore,the transistor is not limited to a transistor having a single-gatestructure; a multi-gate transistor having a plurality of channelformation regions, such as a double-gate transistor may be used.

As the transistor 232 and the transistor 252, a transistor with any of avariety of structures such as a planar type, a FIN-type, and a Tri-Gatetype can be used.

The transistor 232 and the transistor 252 may have the same structure ordifferent structures. However, the size (e.g., channel length andchannel width) or the like of each transistor can be adjusted asappropriate.

The transistor 232 and the transistor 252 each include an electrode 206that can function as a gate electrode, an insulating layer 207 that canfunction as a gate insulating layer, a semiconductor layer 208, anelectrode 214 that can function as one of a source electrode and a drainelectrode, and an electrode 215 that can function as the other of thesource electrode and the drain electrode.

For a conductive material for forming the electrode 206, a metal elementselected from aluminum, chromium, copper, silver, gold, platinum,tantalum, nickel, titanium, molybdenum, tungsten, hafnium (Hf), vanadium(V), niobium (Nb), manganese, magnesium, zirconium, beryllium, and thelike; an alloy containing any of the above metal elements; an alloycontaining a combination of the above metal elements; or the like can beused. Alternatively, a semiconductor having a high electric conductivitytypified by polycrystalline silicon including an impurity element suchas phosphorus, or silicide such as nickel silicide may be used. There isno particular limitation on a formation method of the conductive layer,and a variety of formation methods such as an evaporation method, a CVDmethod, a sputtering method, and a spin coating method can be employed.

The electrode 206 can also be formed using a conductive materialcontaining oxygen, such as indium tin oxide, indium oxide containingtungsten oxide, indium zinc oxide containing tungsten oxide, indiumoxide containing titanium oxide, indium tin oxide containing titaniumoxide, indium zinc oxide, or indium tin oxide to which silicon oxide isadded, or a conductive material containing nitrogen, such as titaniumnitride or tantalum nitride. It is also possible to use a stacked-layerstructure formed using a material containing the above metal element andconductive material containing oxygen. It is also possible to use astacked-layer structure formed using a material containing the abovemetal element and conductive material containing nitrogen. It is alsopossible to use a stacked-layer structure formed using a materialcontaining the above metal element, conductive material containingoxygen, and conductive material containing nitrogen.

The electrode 206 may be formed with a conductive high molecularmaterial (also referred to as conductive polymer). As the conductivehigh molecular material, a π electron conjugated conductive polymer canbe used. For example, polyaniline or a derivative thereof, polypyrroleor a derivative thereof, polythiophene or a derivative thereof, acopolymer of two or more of aniline, pyrrole, and thiophene or aderivative thereof can be used.

The electrode 206 may have a single-layer structure or a stacked-layerstructure of two or more layers. For example, a single-layer structureof an aluminum layer containing silicon, a two-layer structure in whicha titanium layer is stacked over an aluminum layer, a two-layerstructure in which a titanium layer is stacked over a titanium nitridelayer, a two-layer structure in which a tungsten layer is stacked over atitanium nitride layer, a two-layer structure in which a tungsten layeris stacked over a tantalum nitride layer, and a three-layer structure inwhich a titanium layer, an aluminum layer, and a titanium layer arestacked in this order are given. Alternatively, an alloy containing oneor more elements selected from titanium, tantalum, tungsten, molybdenum,chromium, neodymium, and scandium may be used as the electrode 206.

The wiring 219, the electrode 214, and the electrode 215 can be formedat the same time as the electrode 116 using part of the conductivelayers for forming the electrode 116. The insulating layer 207 can beformed using a material and a method similar to those of the insulatinglayer 205. Note that in the case where an organic semiconductor is usedfor the semiconductor layer 208, an organic material such as polyimideor an acrylic resin may be used for the insulating layer 207.

The semiconductor layer 208 can be formed using a single crystalsemiconductor, a polycrystalline semiconductor, a microcrystallinesemiconductor, a nanocrystal semiconductor, a semi-amorphoussemiconductor, an amorphous semiconductor, or the like. For example,amorphous silicon or microcrystalline germanium can be used.Alternatively, a compound semiconductor such as silicon carbide, galliumarsenide, an oxide semiconductor, or a nitride semiconductor, an organicsemiconductor, or the like can be used.

In the case where an organic semiconductor is used for the semiconductorlayer 208, a low molecular organic material having an aromatic ring, aπ-electron conjugated conductive polymer, or the like can be used. Forexample, rubrene, tetracene, pentacene, perylenediimide,tetracyanoquinodimethane, polythiophene, polyacetylene, orpolyparaphenylene vinylene can be used.

In the case of using an oxide semiconductor for the semiconductor layer208, a c-axis aligned crystalline oxide semiconductor (CAAC-OS), apolycrystalline oxide semiconductor, a microcrystalline oxidesemiconductor, a nanocrystalline oxide semiconductor (nc-OS), anamorphous oxide semiconductor, or the like can be used.

Note that an oxide semiconductor has an energy gap as wide as 3.0 eV ormore and high visible-light transmissivity. In a transistor obtained byprocessing an oxide semiconductor under appropriate conditions, it ispossible to realize an extremely low off-state current (current flowingbetween a source and drain in an off state of a transistor). Forexample, the off-state current per 1 μm of a channel width can be lessthan or equal to 100 zA (1×10⁻¹⁹ A), less than or equal to 10 zA(1×10⁻²⁰ A), and further less than or equal to 1 zA (1×10⁻²¹ A) when thesource-drain voltage is 3.5 V at 25° C. Therefore, a display device withlow power consumption can be achieved.

In the case where an oxide semiconductor is used for the semiconductorlayer 208, an insulating layer containing oxygen is preferably used asan insulating layer in contact with the semiconductor layer 208. For theinsulating layer in contact with the semiconductor layer 208, it isparticularly preferable to use an insulating layer from which oxygen isreleased by heat treatment.

An insulating layer 210 is formed over the transistor 232 and thetransistor 252, and an insulating layer 211 is formed over theinsulating layer 210. The insulating layer 210 functions as a protectiveinsulating layer and can prevent or reduce diffusion of impurityelements from a layer above the insulating layer 210 to the transistor232 and the transistor 252. The insulating layer 210 can be formed usinga material and a method similar to those of the insulating layer 205.

An interlayer insulating layer 212 is formed over the insulating layer211. The interlayer insulating layer 212 is able to absorb theunevenness caused by the transistor 232 and the transistor 252.Planarization treatment may be performed on a surface of the interlayerinsulating layer 212. The planarization treatment may be, but notparticularly limited to, polishing treatment (e.g., chemical mechanicalpolishing (CMP)) or dry etching treatment.

Forming the interlayer insulating layer 212 using an insulating materialhaving a planarization function can omit polishing treatment. As theinsulating material having a planarization function, for example, anorganic material such as a polyimide resin or an acrylic resin can beused. Other than the above-described organic materials, it is alsopossible to use a low-dielectric constant material (low-k material) orthe like. Note that the interlayer insulating layer 212 may be formed bystacking a plurality of insulating films formed of these materials.

Over the insulating layer 212, the light-emitting element 125 and thepartition 114 for separating the adjacent light-emitting elements 125are formed.

The substrate 121 is provided with the touch sensor 271 including theelectrode 272, the insulating layer 273, and the electrode 274, thelight-blocking layer 264, the coloring layer 266, and the overcoat layer268. The display device 200 is what is called a top-emissionlight-emitting device, in which light emitted from the light-emittingelement 125 is extracted from the substrate 121 side through thecoloring layer 266.

The light-emitting element 125 is electrically connected to thetransistor 232 through an opening formed in the interlayer insulatinglayer 212, insulating layer 211 and the insulating layer 210.

With a micro optical resonator (also referred to as microcavity)structure which allows light emitted from the EL layer 117 to resonate,lights with different wavelengths and narrowed spectra can be extractedeven when one EL layer 117 is used for different light-emitting elements125.

Note that the manufacturing methods described in Embodiments 1 and 2 andwell-known manufacturing methods can be referred to for manufacturingmethods that are not described in this embodiment.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 4

In this embodiment, a specific structure example of the display device200 is described with reference to FIGS. 37A to 37C. FIG. 37A is a blockdiagram illustrating the structure example of the display device 200.

The display device 200 illustrated in FIG. 37A includes the displayregion 231, a driver circuit 142 a, a driver circuit 142 b, and a drivercircuit 133. The driver circuits 142 a, 142 b, and 133 collectivelycorrespond to the peripheral circuit 251 described in the aboveembodiments. The driver circuits 142 a, 142 b, and 133 may becollectively referred to as a driver circuit portion.

The driver circuits 142 a and 142 b function as, for example, scan linedriver circuits. The driver circuit 133 functions as, for example, asignal line driver circuit. Note that one of the driver circuits 142 aand 142 b may be omitted. Alternatively, some sort of circuit facing thedriver circuit 133 with the display region 231 provided therebetween maybe provided.

The display device 200 includes m wirings 135 that are arrangedsubstantially parallel to each other and whose potentials are controlledby the driver circuit 142 a and/or the driver circuit 142 b, and nwirings 136 that are arranged substantially parallel to each other andwhose potentials are controlled by the driver circuit 133. The displayregion 231 includes a plurality of pixel circuits 134 arranged inmatrix. One pixel circuit 134 is used for driving one subpixel (thepixel 130).

Each of the wirings 135 is electrically connected to the n pixelcircuits 134 in a given row among the pixel circuits 134 arranged in mrows and n columns in the display region 231. Each of the wirings 136 iselectrically connected to the m pixel circuits 134 in a given columnamong the pixel circuits 134 arranged in m rows and n columns Note thatin and n are each an integer of 1 or more.

[Example of Pixel Circuit for Light-Emitting Display Device]

FIGS. 37B and 37C illustrate circuit structures that can be used for thepixel circuits 134 in the display device in FIG. 37A.

The pixel circuit 134 illustrated in FIG. 37B includes a transistor 431,a capacitor 233, the transistor 232, and a transistor 434. The pixelcircuit 134 is electrically connected to the light-emitting element 125.

One of a source electrode and a drain electrode of the transistor 431 iselectrically connected to a wiring to which a data signal is supplied(hereinafter referred to as a signal line DL_n). A gate electrode of thetransistor 431 is electrically connected to a wiring to which a gatesignal is supplied (hereinafter referred to as a scan line GL_m). Thesignal line DL_n and the scan line GL_m correspond to the wiring 136 andthe wiring 135, respectively.

The transistor 431 has a function of controlling whether to write a datasignal to a node 435.

One of a pair of electrodes of the capacitor 233 is electricallyconnected to the node 435, and the other of the pair of electrodes ofthe capacitor 233 is electrically connected to a node 437. The other ofthe source electrode and the drain electrode of the transistor 431 iselectrically connected to the node 435.

The capacitor 233 functions as a storage capacitor for storing datawritten to the node 435.

One of a source electrode and a drain electrode of the transistor 232 iselectrically connected to a potential supply line VL_a, and the other ofthe source electrode and the drain electrode of the transistor 232 iselectrically connected to the node 437. A gate electrode of thetransistor 232 is electrically connected to the node 435.

One of a source electrode and a drain electrode of the transistor 434 iselectrically connected to a potential supply line V0, and the other ofthe source electrode and the drain electrode of the transistor 434 iselectrically connected to the node 437. A gate electrode of thetransistor 434 is electrically connected to the scan line GL_m.

One of an anode and a cathode of the light-emitting element 125 iselectrically connected to a potential supply line VL_b, and the other ofthe anode and the cathode of the light-emitting element 125 iselectrically connected to the node 437.

As the light-emitting element 125, an organic electroluminescent element(also referred to as an organic EL element) or the like can be used, forexample. Note that the light-emitting element 125 is not limited theretoand may be an inorganic EL element containing, for example, an inorganicmaterial.

As a power supply potential, a potential on the comparatively highpotential side or a potential on the comparatively low potential sidecan be used, for example. A power supply potential on the high potentialside is referred to as a high power supply potential (also referred toas VDD), and a power supply potential on the low potential side isreferred to as a low power supply potential (also referred to as VSS). Aground potential can be used as the high power supply potential or thelow power supply potential. For example, in the case where a groundpotential is used as the high power supply potential, the low powersupply potential is a potential lower than the ground potential, and inthe case where a ground potential is used as the low power supplypotential, the high power supply potential is a potential higher thanthe ground potential.

A high power supply potential VDD is supplied to one of the potentialsupply line VL_a and the potential supply line VL_b, and a low powersupply potential VSS is supplied to the other, for example.

In the display device including the pixel circuit 134 in FIG. 37B, thepixel circuits 134 are sequentially selected row by row by the drivercircuit 142 a and/or the driver circuit 142 b, so that the transistors431 and 434 are turned on and a data signal is written to the nodes 435.

When the transistors 431 and 434 are turned off, the pixel circuits 134in which the data has been written to the nodes 435 are brought into aholding state. The amount of current flowing between the sourceelectrode and the drain electrode of the transistor 232 is controlled inaccordance with the potential of the data written to the node 435. Thelight-emitting element 125 emits light with luminance corresponding tothe amount of the flowing current. This operation is sequentiallyperformed row by row; thus, an image can be displayed.

[Example of Pixel Circuit for Liquid Crystal Display Device]

The pixel circuit 134 in FIG. 37C includes the transistor 431 and thecapacitor 233. The pixel circuit 134 is electrically connected to aliquid crystal element 432.

The potential of one of a pair of electrodes of the liquid crystalelement 432 is set in accordance with the specifications of the pixelcircuit 134 as appropriate. The alignment state of the liquid crystalelement 432 depends on data written to a node 436. A common potentialmay be applied to one of the pair of electrodes of the liquid crystalelement 432 included in each of the plurality of pixel circuits 134. Thepotential supplied to one of a pair of electrodes of the liquid crystalelement 432 in the pixel circuit 134 in one row may be different fromthe potential supplied to one of a pair of electrodes of the liquidcrystal element 432 in the pixel circuit 134 in another row.

Examples of a method of driving the display device including the liquidcrystal element 432 include a TN mode, an STN mode, a VA mode, anaxially symmetric aligned micro-cell (ASM) mode, an opticallycompensated birefringence (OCB) mode, a ferroelectric liquid crystal(FLC) mode, an antiferroelectric liquid crystal (AFLC) mode, an MVAmode, a patterned vertical alignment (PVA) mode, an IPS mode, an FFSmode, and a transverse bend alignment (IBA) mode. Other examples of themethod of driving the display device include an electrically controlledbirefringence (ECB) mode, a polymer-dispersed liquid crystal (PDLC)mode, a polymer network liquid crystal (PNLC) mode, and a guest-hostmode. Note that one embodiment of the present invention is not limitedthereto, and various liquid crystal elements and driving methods can beused.

The liquid crystal element 432 may be formed using a liquid crystalcomposition including a liquid crystal exhibiting a blue phase and achiral material. The liquid crystal exhibiting a blue phase has a shortresponse time of 1 ms or less and has optical isotropy; thus, analignment process is not necessary. A liquid crystal display deviceincluding a liquid crystal exhibiting a blue phase has small viewingangle dependence because the liquid crystal has optical isotropy.

In the pixel circuit 134 in the m-th row and the n-th column, one of thesource electrode and the drain electrode of the transistor 431 iselectrically connected to the signal line DL_n, and the other of thesource electrode and the drain electrode of the transistor 431 iselectrically connected to the node 436. The gate electrode of thetransistor 431 is electrically connected to the scan line GL_m. Thetransistor 431 has a function of controlling whether to write a datasignal to the node 436.

One of the pair of electrodes of the capacitor 233 is electricallyconnected to a wiring to which a specific potential is supplied(hereinafter referred to as a capacitor line CL), and the other of thepair of electrodes of the capacitor 233 is electrically connected to thenode 436. The other of the pair of electrodes of the liquid crystalelement 432 is electrically connected to the node 436. The potential ofthe capacitor line CL is set in accordance with the specifications ofthe pixel circuit 134 as appropriate. The capacitor 233 functions as astorage capacitor for storing data written to the node 436.

For example, in the display device including the pixel circuit 134 inFIG. 37C, the pixel circuits 134 are sequentially selected row by row bythe driver circuit 142 a and/or the driver circuit 142 b, so that thetransistors 431 are turned on and a data signal is written to the nodes436.

When the transistors 431 are turned off, the pixel circuits 134 in whichthe data signal has been written to the nodes 436 are brought into aholding state. This operation is sequentially performed row by row;thus, an image can be displayed on the display region 231.

[Display Element]

The display device of one embodiment of the present invention can employvarious modes and can include various elements. The display elementincludes at least one of an electroluminescence (EL) element (e.g., anEL element including organic and inorganic materials, an organic ELelement, or an inorganic EL element) including an LED (e.g., a whiteLED, a red LED, a green LED, or a blue LED), a transistor (a transistorthat emits light depending on current), an electron emitting element, aplasma display panel (PDP), a liquid crystal element, an electrophoreticelement, a display element using micro electro mechanical system (MEMS)such as a grating light valve (GLV), a digital micromirror device (DMD),a digital micro shutter (DMS) element, a MIRASOL (registered trademark)display, an interferometric modulator display (IMOD) element, and apiezoelectric ceramic display, an electrowetting element, and the like.Other than the above, display device may contain a display medium whosecontrast, luminance, reflectance, transmittance, or the like is changedby electrical or magnetic action. Alternatively, quantum dots may beused as the display element. Examples of display devices includingquantum dots include a quantum dot display. Examples of display deviceshaving EL elements include an EL display. Examples of a display deviceincluding an electron emitter include a field emission display (FED) andan SED-type flat panel display (SED: surface-conduction electron-emitterdisplay). Examples of display devices including liquid crystal elementsinclude a liquid crystal display (e.g., a transmissive liquid crystaldisplay, a transflective liquid crystal display, a reflective liquidcrystal display, a direct-view liquid crystal display, or a projectionliquid crystal display). Examples of display devices havingelectrophoretic elements include electronic paper. In the case of atransflective liquid crystal display or a reflective liquid crystaldisplay, some or all of pixel electrodes function as reflectiveelectrodes. For example, some or all of pixel electrodes are formed tocontain aluminum, silver, or the like. In such a case, a memory circuitsuch as an SRAM can be provided under the reflective electrodes, leadingto lower power consumption.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 5

In this embodiment, an example of a transistor which can be used insteadof the transistor 232 and/or the transistor 252 described in the aboveembodiments is described with reference to FIGS. 38A1, 38A2, 38B1, and38B2. A transistor disclosed in this specification and the like can beapplied to the transistors 431, 434, and the like.

[Bottom-Gate Transistor]

A transistor 410 shown in FIG. 38A1 as an example is achannel-protective transistor that is a type of bottom-gate transistor.The transistor 410 includes an insulating layer 209 that can function asa channel protective layer over a channel formation region in thesemiconductor layer 208. The insulating layer 209 can be formed using amaterial and a method that are similar to those of the insulating layer205. Part of the electrode 214 and part of the electrode 215 are formedover the insulating layer 209.

With the insulating layer 209 provided over the channel formationregion, the semiconductor layer 208 can be prevented from being exposedat the time of forming the electrode 214 and the electrode 215. Thus,the semiconductor layer 208 can be prevented from being reduced inthickness at the time of forming the electrode 214 and the electrode215.

A transistor 411 illustrated in FIG. 38A2 is different from thetransistor 410 in that an electrode 213 that can function as a back gateelectrode is provided over the insulating layer 211. The electrode 213can be formed using a material and a method that are similar to those ofthe electrode 206. The electrode 213 may be formed between theinsulating layer 210 and the insulating layer 211.

In general, the back gate electrode is formed using a conductive layerand positioned so that the channel formation region of the semiconductorlayer is provided between the gate electrode and the back gateelectrode. Thus, the back gate electrode can function in a mannersimilar to that of the gate electrode. The potential of the back gateelectrode may be the same as that of the gate electrode or may be a GNDpotential or a predetermined potential. By changing a potential of theback gate electrode independently of the potential of the gateelectrode, the threshold voltage of the transistor can be changed.

The electrodes 206 and 213 can both function as a gate electrode. Thus,the insulating layers 207, 209, 210, and 211 can all function as a gateinsulating layer.

In the case where one of the electrode 206 and the electrode 213 issimply referred to as a “gate electrode”, the other can be referred toas a “back gate electrode”. For example, in the transistor 411, in thecase where the electrode 213 is referred to as a “gate electrode”, theelectrode 206 is referred to as a “back gate electrode”. In the casewhere the electrode 213 is used as a “gate electrode”, the transistor411 is a kind of bottom-gate transistor. Furthermore, one of theelectrode 206 and the electrode 213 may be referred to as a “first gateelectrode”, and the other may be referred to as a “second gateelectrode”.

By providing the electrode 206 and the electrode 213 with thesemiconductor layer 208 provided therebetween and setting the potentialsof the electrode 206 and the electrode 213 to be the same, a region ofthe semiconductor layer 208 through which carriers flow is enlarged inthe film thickness direction; thus, the number of transferred carriersis increased. As a result, the on-state current and the field-effectmobility of the transistor 411 are increased.

Therefore, the transistor 411 has large on-state current for the areaoccupied thereby. That is, the area occupied by the transistor 411 canbe small for required on-state current.

Furthermore, the gate electrode and the back gate electrode are formedusing conductive layers and thus each have a function of preventing anelectric field generated outside the transistor from influencing thesemiconductor layer in which the channel is formed (in particular, afunction of blocking static electricity).

Since the electrode 206 and the electrode 213 each have a function ofblocking an electric field generated outside, charges of chargedparticles and the like generated on the substrate 111 side or above theelectrode 213 do not influence the channel formation region in thesemiconductor layer 208. Therefore, degradation in a stress test (e.g.,a negative gate bias temperature (−GBT) stress test in which negativecharges are applied to a gate) can be reduced, and changes in the risingvoltages of on-state current at different drain voltages can besuppressed. Note that this effect is caused when the electrodes 206 and213 have the same potential or different potentials.

The BT stress test is one kind of accelerated test and can evaluate, ina short time, a change by long-term use (i.e., a change over time) incharacteristics of transistors. In particular, the change in thresholdvoltage of the transistor between before and after the BT stress test isan important indicator when examining the reliability of the transistor.If the change in the threshold voltage between before and after the BTstress test is small, the transistor has higher reliability.

By providing the electrode 206 and the electrode 213 and setting thepotentials of the electrode 206 and the electrode 213 to be the same,the change in threshold voltage is reduced. Accordingly, variation inelectrical characteristics among a plurality of transistors is alsoreduced.

The transistor including the back gate electrode has a smaller change inthreshold voltage between before and after a positive GBT stress test inwhich positive charges are applied to a gate than a transistor includingno back gate electrode.

When the back gate electrode is formed using a light-blocking conductivefilm, light can be prevented from entering the semiconductor layer fromthe back gate electrode side. Therefore, photodegradation of thesemiconductor layer can be prevented and deterioration in electricalcharacteristics of the transistor, such as a shift of the thresholdvoltage, can be prevented.

A transistor 420 shown in FIG. 38B1 as an example is achannel-protective transistor that is a type of bottom-gate transistor.The transistor 420 has substantially the same structure as thetransistor 410 but is different from the transistor 410 in that theinsulating layer 209 covers the side surfaces of the semiconductor layer208. The semiconductor layer 208 is electrically connected to theelectrode 214 in an opening which is formed by selectively removing partof the insulating layer 209. The semiconductor layer 208 is electricallyconnected to the electrode 215 in the opening which is formed byselectively removing part of the insulating layer 209. A region of theinsulating layer 209 which overlaps with the channel formation regioncan function as a channel protective layer.

A transistor 421 illustrated in FIG. 38B2 is different from thetransistor 420 in that the electrode 213 that can function as a backgate electrode is provided over the insulating layer 211.

With the insulating layer 209, the semiconductor layer 208 can beprevented from being exposed at the time of forming the electrode 214and the electrode 215. Thus, the semiconductor layer 208 can beprevented from being reduced in thickness at the time of forming theelectrode 214 and the electrode 215.

The length between the electrode 214 and the electrode 206 and thelength between the electrode 215 and the electrode 206 in thetransistors 420 and 421 are longer than those in the transistors 410 and411. Thus, the parasitic capacitance generated between the electrode 214and the electrode 206 can be reduced. Moreover, the parasiticcapacitance generated between the electrode 215 and the electrode 206can be reduced.

[Top-Gate Transistor]

A transistor 430 shown in FIG. 39A1 as an example is a type of top-gatetransistor. The transistor 430 includes the semiconductor layer 208 overthe insulating layer 119; the electrode 214 in contact with part of thesemiconductor layer 208 and the electrode 215 in contact with part ofthe semiconductor layer 208, over the semiconductor layer 208 and theinsulating layer 119; the insulating layer 207 over the semiconductorlayer 208, the electrode 214 and the electrode 215; and the electrode206 over the insulating layer 207. The insulating layer 210 and theinsulating layer 211 are formed over the electrode 206.

Since, in the transistor 430, the electrode 206 overlaps with neitherthe electrode 214 nor the electrode 215, the parasitic capacitancegenerated between the electrode 206 and the electrode 214 and theparasitic capacitance generated between the electrode 206 and theelectrode 215 can be reduced. After the formation of the electrode 206,an impurity element 221 is introduced into the semiconductor layer 208using the electrode 206 as a mask, so that an impurity region can beformed in the semiconductor layer 208 in a self-aligned manner (see FIG.39A3).

The introduction of the impurity element 221 can be performed with anion implantation apparatus, an ion doping apparatus, or a plasmatreatment apparatus.

As the impurity element 221, for example, at least one element of aGroup 13 element and a Group 15 element can be used. In the case wherean oxide semiconductor is used for the semiconductor layer 208, it ispossible to use at least one kind of element of a rare gas, hydrogen,and nitrogen as the impurity element 221.

A transistor 431 illustrated in FIG. 39A2 is different from thetransistor 430 in that the electrode 213 and an insulating layer 217 areincluded. The transistor 431 includes the electrode 213 formed over theinsulating layer 119 and the insulating layer 217 formed over theelectrode 213. As described above, the electrode 213 can function as aback gate electrode. Thus, the insulating layer 217 can function as agate insulating layer. The insulating layer 217 can be formed using amaterial and a method that are similar to those of the insulating layer205.

The transistor 431 as well as the transistor 411 has large on-statecurrent for the area occupied thereby. That is, the area occupied by thetransistor 431 can be small for required on-state current. According toone embodiment of the present invention, the area occupied by atransistor can be reduced. Therefore, according to one embodiment of thepresent invention, a semiconductor device having a high degree ofintegration can be provided.

A transistor 440 shown in FIG. 39B1 as an example is a type of top-gatetransistor. The transistor 440 is different from the transistor 430 inthat the semiconductor layer 208 is formed after the formation of theelectrode 214 and the electrode 215. A transistor 441 shown in FIG. 39B2as an example is different from the transistor 440 in that it includesthe electrode 213 and the insulating layer 217. Thus, in the transistors440 and 441, part of the semiconductor layer 208 is formed over theelectrode 214 and another part of the semiconductor layer 208 is formedover the electrode 215.

The transistor 441 as well as the transistor 411 has large on-statecurrent for the area occupied thereby. That is, the area occupied by thetransistor 441 can be small for required on-state current. According toone embodiment of the present invention, the area occupied by atransistor can be reduced. Therefore, according to one embodiment of thepresent invention, a semiconductor device having a high degree ofintegration can be provided.

In the transistors 440 and 441, after the formation of the electrode206, the impurity element 221 is introduced into the semiconductor layer208 using the electrode 206 as a mask, so that an impurity region can beformed in the semiconductor layer 208 in a self-aligned manner.

[S-Channel Transistor]

FIG. 40A is a top view of a transistor 450. FIG. 40B is across-sectional view (in the channel length direction) taken along thedashed-dotted line X1-X2 in FIG. 40A. FIG. 40C is a cross-sectional view(in the channel width direction) taken along the dashed-dotted lineY1-Y2 in FIG. 40A.

A semiconductor layer 242 is provided over a projecting portion of theinsulating layer 109, in which case the electrode 243 can cover a sidesurface of the semiconductor layer 242. That is, the transistor 450 hasa structure in which the semiconductor layer 242 is electricallysurrounded by an electric field of the electrode 243. Such a structureof a transistor in which a semiconductor is electrically surrounded byan electric field of a conductive film is referred to as a surroundedchannel (s-channel) structure. A transistor having an s-channelstructure is referred to as an s-channel transistor.

In the s-channel transistor, a channel is formed in the whole (bulk) ofthe semiconductor layer 242 in some cases. In the s-channel transistor,the drain current of the transistor can be increased, so that a largeramount of on-state current can be obtained. Therefore, the area occupiedby the transistor can be reduced, which leads to high definition of adisplay device and high integration of a semiconductor device.

Furthermore, the entire channel formation region of the semiconductorlayer 242 can be depleted by the electric field of the electrode 243.Accordingly, the off-state current of the s-channel transistor can befurther reduced. Therefore, power consumption of a display device and asemiconductor device can be reduced.

When the projecting portion of the insulating layer 109 is increased inheight, and the channel width is shortened, the effects of the s-channelstructure to increase the on-state current and reduce the off-statecurrent can be enhanced.

As in a transistor 451 illustrated in FIGS. 41A to 41C, the electrode213 may be provided under the semiconductor layer 242 with an insulatinglayer positioned therebetween. FIG. 41A is a top view of a transistor451. FIG. 41B is a cross-sectional view taken along the dashed-dottedline X1-X2 in FIG. 41A. FIG. 41C is a cross-sectional view taken alongthe dashed-dotted line Y1-Y2 in FIG. 41A.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 6

Although a capacitive touch sensor is used as an example of the touchsensor 271 in the above embodiments, one embodiment of the presentinvention is not limited thereto. A resistive touch sensor may be usedas the touch sensor 271. Examples of the capacitive touch sensor are ofa surface capacitive type and of a projected capacitive type.Alternatively, an active matrix touch sensor using an active elementsuch as a transistor can be used.

In this embodiment, a structure and a driving method of an active matrixtouch sensor 500 that can be used as the touch sensor 271 are describedwith reference to FIGS. 42A to 42D2 and FIGS. 43A to 43D.

FIG. 42A is a block diagram illustrating the structure of the activematrix touch sensor 500. FIG. 42B is a circuit diagram illustrating astructure of a convertor CONV. FIG. 42C is a circuit diagramillustrating a structure of a sensing unit 510. FIGS. 42D1 and 42D2 aretiming charts showing a method of driving the sensing unit 510.

FIG. 43A is a block diagram illustrating the structure of an activematrix touch sensor 500B. FIG. 43B is a circuit diagram illustrating astructure of a convertor CONY. FIG. 43C is a circuit diagramillustrating a structure of a sensing unit 510B. FIG. 43D is a timingchart showing a method of driving the sensing unit 510B.

<Structure Example 1 of Positional Data Input Portion>

The touch sensor 500 illustrated in FIGS. 42A to 42D includes thesensing units 510 arranged in a matrix; scan lines G1 to which thesensing units 510 arranged in the row direction are electricallyconnected; and signal lines DL to which the sensing units 510 arrangedin the column direction are electrically connected (see FIG. 42A).

For example, the sensing units 510 can be arranged in a matrix of n rowsand m columns (each of n and m is a natural number greater than or equalto 1).

The sensing unit 510 includes a sensor element 518 that functions as acapacitor and a sensor circuit 519. A first electrode of the sensorelement 518 is electrically connected to a wiring CS. A second electrodeof the sensor element 518 is electrically connected to a node A. Withthis structure, a potential of the node A can be controlled by a controlsignal supplied by the wiring CS.

<<Sensor Circuit 519>>

The sensor circuit 519 illustrated in FIG. 42C includes a transistor M1,a transistor M2, and a transistor M3. A gate of the transistor M1 iselectrically connected to the node A. One of a source and a drain of thetransistor M1 is electrically connected to a wiring VPI that can supplythe ground potential. The other of the source and the drain iselectrically connected to one of a source and a drain of the transistorM2.

The other of the source and the drain of the transistor M2 iselectrically connected to the signal line DL that can supply a sensingsignal DATA. A gate of the transistor M2 is electrically connected to ascan line G1 that can supply a selection signal.

One of a source and a drain of the transistor M3 is electricallyconnected to the node A. The other of the source and the drain iselectrically connected to a wiring VRES that can supply a potential thatturns on the transistor M1. A gate of the transistor M3 is electricallyconnected to a wiring RES that can supply a reset signal.

The capacitance of the sensor element 518 varies, for example, when anobject gets closer to the first electrode or the second electrode of thesensor element 518 (the node A) or when a gap between the first andsecond electrodes is changed. Thus, the sensing unit 510 can supply thesensing signal DATA in accordance with a change in the capacitance ofthe sensor element 518.

The wiring VRES and the wiring VPI can supply, for example, a groundpotential. A wiring VPO and a wiring BR can supply, for example, a highpower supply potential.

The wiring RES can supply a reset signal. The scan line G1 can supply aselection signal. The wiring CS can supply a control signal forcontrolling the potential of the second electrode (the potential of thenode A) of the sensor element 518.

The signal line DL can supply the sensing signal DATA. A terminal OUTcan supply a signal obtained by conversion based on the sensing signalDATA.

<<Converter CONV>>

The convertor CONV includes a conversion circuit. Any of variouscircuits that can convert the sensing signal DATA and supply a signalobtained by the conversion to the terminal OUT can be used for theconverter CONV. The converter CONV may be electrically connected to thesensing circuit 519 to form a source follower circuit, a current mirrorcircuit, or the like, for example.

Specifically, a source follower circuit can be formed using theconverter CONV including a transistor M4 (see FIG. 42B). Note that thetransistor M4 may be formed in the same process as the transistors M1 toM3.

Any of the transistors described in the above embodiments can be used asthe transistors M1 to M4. For example, a Group 4 element, a compoundsemiconductor, or an oxide semiconductor can be used for thesemiconductor layer. Specifically, a silicon-containing semiconductor, agallium arsenide-containing semiconductor, an indium-containing oxidesemiconductor, or the like can be used.

The convertor CONV and a driver circuit GD may be provided on anothersubstrate (e.g., a single-crystal semiconductor substrate or apolycrystalline semiconductor substrate) and electrically connected tothe sensing unit 510 by a chip on glass (COG) method, a wire bondingmethod, or the like, or using an FPC or the like.

<Driving Method of Sensing Circuit 519>

The driving method of the sensing circuit 519 is described.

<<First Step>>

In a first step, after the transistor M3 is turned on, a reset signalfor turning off the transistor M3 is supplied to the gate of thetransistor M3, so that the potential of the node A is set to apredetermined potential (see Period T1 in FIG. 42D1).

Specifically, the reset signal is supplied to the gate of the transistorM3 via the wiring RES. The transistor M3 to which the reset signal issupplied sets the potential of the node A to a potential at which thetransistor M1 is turned off, for example (see Period T1 in FIG. 42D1).

<<Second Step>>

In a second step, a selection signal for turning on the transistor M2 issupplied, so that the other of the source and the drain of thetransistor M1 is electrically connected to the signal line DL.

Specifically, the selection signal is supplied to the gate of thetransistor M2 via the scan line G1. The transistor M2 to which theselection signal is supplied makes the other of the source and the drainof the transistor M1 electrically connected to the signal line DL (seePeriod T2 in FIG. 42D1).

<<Third Step>>

In a third step, a control signal is supplied to the first electrode ofthe sensor element 518, and a control signal and the potential thatvaries depending on the electrostatic capacitance of the sensor element518 are supplied to the gate of the transistor M1 via the node A.

Specifically, a rectangular control signal is supplied to the wiring CS.The sensor element 518 the first electrode of which is supplied with therectangular control signal increases the potential of the node A inaccordance with the electrostatic capacitance of the sensor element 518(see the latter part of Period T2 in FIG. 42D1).

For example, when the sensor element 518 is placed in the air and anobject having a higher dielectric constant than the air is placed in theproximity of the first electrode of the sensor element 518, the apparentelectrostatic capacitance of the sensor element 518 is increased. Inthis case, a change in the potential of the node A caused by therectangular control signal is smaller than that when an object having ahigher dielectric constant than the air is not placed in the proximityof the first electrode of the sensor element 518 (see a solid line inFIG. 42D2).

<<Fourth Step>>

In a fourth step, a signal caused by a change in the potential of thegate of the transistor M1 is supplied to the signal line DL.

For example, a change in current caused by a change in the potential ofthe gate of the transistor M1 is supplied to the signal line DL.

The converter CONV converts a change in current flowing through thesignal line DL into a voltage change and supplies the voltage change tothe terminal OUT.

<<Fifth Step>>

In a fifth step, a selection signal for turning off the transistor M2 issupplied to the gate of the transistor M2.

Each of the scan lines G1(1) to G1(n) performs the first to fifth steps;thus, which region in the touch sensor 500 is selected can be sensed.

<Structure Example 2 of Positional Data Input Portion>

The touch sensor 500B illustrated in FIGS. 43A to 43D is different fromthe touch sensor 500 in that the touch sensor 500B includes the sensingunit 510B instead of the sensing unit 510.

The sensing unit 510B is different from the sensing unit 510 in thefollowing points: the first electrode of the sensor element 518 in thesensing unit 510B is electrically connected to the scan line G1 whilethat in the sensing unit 510 is electrically connected to the wiring CS;and the other of the source and the drain of the transistor M1 in thesensing unit 510B is electrically connected to the signal line DL notvia the transistor M2 while that in the sensing unit 510 is electricallyconnected to the signal line DL via the transistor M2. Here, differentstructures are described in detail, and the above description isreferred to for the other similar structures.

The touch sensor 500B includes the sensing units 510B arranged in amatrix; scan lines G1 to which the sensing units 510B arranged in therow direction are electrically connected; and signal lines DL to whichthe sensing units 510B arranged in the column direction are electricallyconnected (see FIG. 43A).

For example, the sensing units 510B can be arranged in a matrix of nrows and m columns (each of n and m is a natural number greater than orequal to 1).

The sensing unit 510B includes the sensor element 518, and the firstelectrode of the sensor element 518 is electrically connected to thescan line G1. With this structure, a selected scan line G1 can controlthe potentials of the nodes A of the sensing units 510B to which theselected scan line G1 is electrically connected, by supplying theselection signal.

The signal line DL and the scan line G1 may be formed with the sameconductive film.

The first electrode of the sensor element 518 and the scan line G1 maybe formed with the same conductive film. For example, the firstelectrodes of the sensor elements 518 included in the sensing units 510Barranged in the row direction may be connected and the connectedelectrodes may be used as the scan line G1.

<<Sensor Circuit 519B>>

The sensor circuit 519B illustrated in FIG. 43C includes the transistorM1 and the transistor M3. A gate of the transistor M1 is electricallyconnected to the node A. One of a source and a drain of the transistorM1 is electrically connected to a wiring VPI that can supply the groundpotential. The other of the source and the drain is electricallyconnected to the signal line DL that can supply the sensing signal DATA.

One of the source and the drain of the transistor M3 is electricallyconnected to the node A. The other of the source and the drain iselectrically connected to the wiring VRES that can supply a potentialthat turns on the transistor M1. The gate of the transistor M3 iselectrically connected to the wiring RES that can supply a reset signal.

The capacitance of the sensor element 518 varies, for example, when anobject gets closer to the first electrode or the second electrode of thesensor element 518 (the node A) or when a gap between the first andsecond electrodes is changed. Thus, the sensing unit 510 can supply thesensing signal DATA in accordance with a change in the capacitance ofthe sensor element 518.

The wiring VRES and the wiring VPI can supply, for example, a groundpotential. A wiring VPO and a wiring BR can supply, for example, a highpower supply potential.

The wiring RES can supply the reset signal, and the scan line G1 cansupply the selection signal.

The signal line DL can supply the sensing signal DATA. The terminal OUTcan supply a signal obtained by conversion based on the sensing signalDATA.

<Driving Method of Sensing Circuit 519B>

The driving method of the sensing circuit 519B is described.

<<First Step>>

In a first step, after the transistor M3 is turned on, a reset signalfor turning off the transistor M3 is supplied to the gate of thetransistor M3, so that the potential of the first electrode of thesensor element 518 is set to a predetermined potential (see Period T1 inFIG. 43D).

Specifically, the reset signal is supplied via the wiring RES. Thetransistor M3 to which the reset signal is supplied sets the potentialof the node A to a potential at which the transistor M1 is turned off,for example (see FIG. 43C).

<<Second Step>>

In a second step, a selection signal is supplied to the first electrodeof the sensor element 518, and a selection signal and the potential thatvaries depending on the electrostatic capacitance of the sensor element518 are supplied to the gate of the transistor M1 via the node A (seePeriod T2 in FIG. 43D).

Specifically, a rectangular selection signal is supplied to the scanline G1(i−1). The sensor element 518 the first electrode of which issupplied with the rectangular selection signal increases the potentialof the node A in accordance with the electrostatic capacitance of thesensor element 518.

For example, when the sensor element 518 is placed in the air and anobject having a higher dielectric constant than the air is placed in theproximity of the first electrode of the sensor element 518, the apparentelectrostatic capacitance of the sensor element 518 is increased. Inthis case, a change in the potential of the node A caused by therectangular selection signal is smaller than that when an object havinga higher dielectric constant than the air is not placed in the proximityof the first electrode of the sensor element 518.

<<Third Step>>

In a third step, a signal caused by a change in the potential of thegate of the transistor M1 is supplied to the signal line DL.

For example, a change in current caused by a change in the potential ofthe gate of the transistor M1 is supplied to the signal line DL.

The converter CONV converts a change in current flowing through thesignal line DL into a voltage change and supplies the voltage change tothe terminal OUT.

Each of the scan lines G1(1) to G1(n) performs the first to third steps(see Periods T2 to T4 in FIG. 43D). In FIG. 43D, the scan line G1 in thei-th row (i is a natural number of 1 to n) is expressed as the scan lineG1(i). According to the above-described structural and operationexamples, which region in the touch sensor 500B is selected can besensed.

In the active matrix touch sensor, signal supply to the sensing unit 510that is not needed for sensing can be stopped by a transistor. This canreduce interference to a selected sensing unit 510 by a non-selectedsensing unit 510. Accordingly, the active matrix touch sensor can havehigh resistance to noise and high detection sensitivity.

Since the active matrix touch sensor can have high detectionsensitivity, even when the sensing unit 510 or the sensor element 518 isreduced in size, a selected region can be detected with high accuracy.Therefore, in the active matrix touch sensor, the number of sensingunits 510 per unit area (surface density) can be increased. Thus, theactive matrix touch sensor can have high accuracy of detecting theposition of a selected region.

The active matrix touch sensor can be a touch sensor of various sizes,for example, a hand-held touch sensor or a touch sensor that can be usedin an electronic blackboard. In particular, the entire detection regionin the active matrix touch sensor can be increased easily as comparedwith the other touch sensors. The use of the active matrix touch sensorenables a large-area touch sensor with high resolution.

Embodiment 7

In this embodiment, structure examples of a light-emitting element thatcan be used as the light-emitting element 125 are described. Note thatan EL layer 320 described in this embodiment corresponds to the EL layer117 described in the other embodiments.

<Structure of Light-Emitting Element>

In a light-emitting element 330 illustrated in FIG. 44A, the EL layer320 is sandwiched between a pair of electrodes (electrodes 318 and 322).The electrode 318, the electrode 322, and the EL layer 320 respectivelycorrespond to the electrode 115, the electrode 118, and the EL layer 117of the aforementioned Embodiments. Note that the electrode 318 is usedas an anode and the electrode 322 is used as a cathode as an example inthe following description of this embodiment.

The EL layer 320 includes at least a light-emitting layer and may have astacked-layer structure including a functional layer other than thelight-emitting layer. As the functional layer other than thelight-emitting layer, a layer containing a substance having a highhole-injection property, a substance having a high hole-transportproperty, a substance having a high electron-transport property, asubstance having a high electron-injection property, a bipolar substance(a substance having high electron and hole transport properties), or thelike can be used. Specifically, functional layers such as ahole-injection layer, a hole-transport layer, an electron-transportlayer, and an electron-injection layer can be used in appropriatecombination.

The light-emitting element 330 illustrated in FIG. 44A emits light whencurrent flows by applying a potential difference between the electrode318 and the electrode 322 and holes and electrons are recombined in theEL layer 320. In other words, a light-emitting region is formed in theEL layer 320.

In one embodiment of the present invention, light emitted from thelight-emitting element 330 is extracted to the outside from theelectrode 318 side or the electrode 322 side. Thus, one of theelectrodes 318 and 322 is formed using a light-transmitting substance.

Note that a plurality of EL layers 320 may be stacked between theelectrode 318 and the electrode 322 as in a light-emitting element 331illustrated in FIG. 44B. In the case where n (n is a natural number of 2or more) layers are stacked, an electric charge generation layer 320 ais preferably provided between an m-th EL layer 320 and an (m+1)th ELlayer 320. Note that in is a natural number greater than or equal to 1and less than n. The components other than the electrode 318 and theelectrode 322 correspond to the EL layer 117 of the aforementionedEmbodiments.

The electric charge generation layer 320 a can be formed using acomposite material of an organic compound and a metal oxide. Examples ofthe metal oxide are vanadium oxide, molybdenum oxide, tungsten oxide, orthe like. As the organic compound, a variety of compounds can be used;for example, an aromatic amine compound, a carbazole derivative, anaromatic hydrocarbon, and an oligomer, a dendrimer, and a polymer havinga basic skeleton of these compounds can be used. Note that as theorganic compound, it is preferable to use an organic compound that has ahole-transport property and has a hole mobility of 10⁻⁶ cm²/Vs orhigher. However, other substances may be used as long as theirhole-transport properties are higher than their electron-transportproperties. These materials used for the electric charge generationlayer 320 a have excellent carrier-injection properties andcarrier-transport properties; thus, the light-emitting element 330 canbe driven with low current and with low voltage. Other than thecomposite material, the metal oxide, a composite material of an organiccompound and an alkali metal, an alkaline earth metal, or a compound ofthe alkali metal or the alkaline earth metal can be used in the electriccharge generation layer 320 a.

Note that the electric charge generation layer 320 a may be formed by acombination of a composite material of an organic compound and a metaloxide with another material. For example, the electric charge generationlayer 320 a may be formed by a combination of a layer containing thecomposite material of an organic compound and a metal oxide with a layercontaining one compound selected from electron-donating substances and acompound having a high electron-transport property. Furthermore, theelectric charge generation layer 320 a may be formed by a combination ofa layer containing the composite material of an organic compound and ametal oxide with a transparent conductive film.

The light-emitting element 331 having such a structure is unlikely toresult in energy transfer between the neighboring EL layer 320 and caneasily realize high emission efficiency and a long lifetime.Furthermore, it is easy to obtain phosphorescence from onelight-emitting layer and fluorescence from the other light-emittinglayer.

The electric charge generation layer 320 a has a function of injectingholes to one of the EL layers 320 that is in contact with the electriccharge generation layer 320 a and a function of injecting electrons tothe other EL layer 320 that is in contact with the electric chargegeneration layer 320 a, when voltage is applied to the electrodes 318and 322.

The light-emitting element 331 illustrated in FIG. 44B can provide avariety of emission colors by changing the type of the light-emittingsubstance used for the EL layers 320. In addition, a plurality oflight-emitting substances having different emission colors may be usedas the light-emitting substances, so that light emission having a broadspectrum or white light emission can be obtained.

In the case of obtaining white light emission using the light-emittingelement 331 in FIG. 44B, as for a combination of a plurality of ELlayers, a structure for emitting white light including red light, bluelight, and green light may be used. For example, the structure mayinclude an EL layer containing a blue fluorescent substance as alight-emitting substance and an EL layer containing green and redphosphorescent substances as light-emitting substances. Alternatively,the structure may include an EL layer emitting red light, an EL layeremitting green light, and an EL emitting blue light. Furtheralternatively, with a structure including EL layers emitting light ofcomplementary colors, white light emission can be obtained. In astacked-layer element including two EL layers which emit lights withcomplementary colors, the combinations of colors are as follows: blueand yellow, blue-green and red, and the like.

Note that in the structure of the above stacked-layer element, byproviding the electric charge generation layer between the stackedlight-emitting layers, the element can give a high-luminance region at alow current density, and have a long lifetime.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

Embodiment 8

In this embodiment, examples of an electronic device including thedisplay device of one embodiment of the present invention are describedwith reference to drawings.

Specific examples of the electronic device that uses the display deviceof one embodiment of the present invention are as follows: displaydevices of televisions, monitors, and the like, lighting devices,desktop and laptop personal computers, word processors, imagereproduction devices which reproduce still images and moving imagesstored in recording media such as digital versatile discs (DVDs),portable CD players, radios, tape recorders, headphone stereos, stereos,table clocks, wall clocks, cordless phone handsets, transceivers, mobilephones, car phones, portable game machines, tablet terminals, large gamemachines such as pachinko machines, calculators, portable informationterminals, electronic notebooks, e-book readers, electronic translators,audio input devices, video cameras, digital still cameras, electricshavers, high-frequency heating appliances such as microwave ovens,electric rice cookers, electric washing machines, electric vacuumcleaners, water heaters, electric fans, hair dryers, air-conditioningsystems such as air conditioners, humidifiers, and dehumidifiers,dishwashers, dish dryers, clothes dryers, futon dryers, electricrefrigerators, electric freezers, electric refrigerator-freezers,freezers for preserving DNA, flashlights, electrical tools such as achain saw, smoke detectors, and medical equipment such as dialyzers.Other examples are as follows: industrial equipment such as guidelights, traffic lights, conveyor belts, elevators, escalators,industrial robots, power storage systems, and power storage devices forleveling the amount of power supply and smart grid. In addition, movingobjects and the like driven by electric motors using power from a powerstorage unit are also included in the category of electronic devices.Examples of the moving objects include electric vehicles (EV), hybridelectric vehicles (HEV) which include both an internal-combustion engineand a motor, plug-in hybrid electric vehicles (PHEV), tracked vehiclesin which caterpillar tracks are substituted for wheels of thesevehicles, motorized bicycles including motor-assisted bicycles,motorcycles, electric wheelchairs, golf carts, boats, ships, submarines,helicopters, aircrafts, rockets, artificial satellites, space probes,planetary probes, and spacecrafts.

In particular, as examples of electronic devices including the displaydevice of one embodiment of the present invention, the following can begiven: television devices (also referred to as televisions or televisionreceivers), monitors of computers or the like, digital cameras, digitalvideo cameras, digital photo frames, mobile phones (also referred to ascellular phones or mobile phone devices), portable game machines,portable information terminals, audio reproducing devices, large gamemachines such as pachinko machines, and the like.

In addition, a lighting device or a display device can be incorporatedalong a curved inside/outside wall surface of a house or a building or acurved interior/exterior surface of a car.

FIG. 45A is an example of a mobile phone (e.g., a smartphone). A mobilephone 7400 includes a display portion 7402 that is incorporated in ahousing 7401. The mobile phone 7400 further includes operation buttons7403, an external connection port 7404, a speaker 7405, a microphone7406, and the like. The mobile phone 7400 is manufactured using thedisplay device of one embodiment of the present invention for thedisplay portion 7402.

The mobile phone 7400 illustrated in FIG. 45A includes a touch sensor inthe display portion 7402. When the display portion 7402 is touched witha finger or the like, data can be input into the mobile phone 7400.Furthermore, operations such as making a call and inputting a letter canbe performed by touch on the display portion 7402 with a finger or thelike.

With the operation buttons 7403, power ON/OFF can be switched. Inaddition, types of images displayed on the display portion 7402 can beswitched; for example, switching images from a mail creation screen to amain menu screen.

Here, the display portion 7402 includes the display device of oneembodiment of the present invention. Thus, the mobile phone can have acurved display portion and high reliability.

FIG. 45B illustrates an example of a mobile phone (e.g., smartphone). Amobile phone 7410 includes a housing 7411 provided with a displayportion 7412, a microphone 7416, a speaker 7415, a camera 7417, anexternal connection portion 7414, an operation button 7413, and thelike. In the case where a display device of one embodiment of thepresent invention is manufactured using a flexible substrate, thedisplay device can be used for the display portion 7412 with a curvedsurface.

When the display portion 7412 of the cellular phone 7410 illustrated inFIG. 45B is touched with a finger or the like, data can be input to thecellular phone 7410. Operations such as making a call and creating ane-mail can be performed by touching the display portion 7412 with afinger or the like.

There are mainly three screen modes of the display portion 7412. Thefirst mode is a display mode mainly for displaying an image. The secondmode is an input mode mainly for inputting data such as characters. Thethird mode is a display-and-input mode in which two modes of the displaymode and the input mode are combined.

For example, in the case of making a call or creating e-mail, acharacter input mode mainly for inputting characters is selected for thedisplay portion 7412 so that characters displayed on the screen can beinput. In this case, it is preferable to display a keyboard or numberbuttons on almost the entire screen of the display portion 7412.

The screen modes can be switched depending on the kind of imagesdisplayed on the display portion 7412. For example, when a signal of animage displayed on the display portion is a signal of moving image data,the screen mode may be switched to the display mode. When the signal isa signal of text data, the screen mode may be switched to the inputmode.

In the input mode, if a touch sensor in the display portion 7412 judgesthat the input by touch on the display portion 7412 is not performed fora certain period, the screen mode may be switched from the input mode tothe display mode.

When a detection device including a sensor (e.g., a gyroscope or anacceleration sensor) is provided inside the mobile phone 7410, thedirection of display on the screen of the display portion 7412 can beautomatically changed by determining the orientation of the mobile phone7410 (whether the mobile phone is placed horizontally or vertically).Furthermore, the direction of display on the screen can be changed bytouch on the display portion 7412 or operation with the operation button7413 of the housing 7411.

FIG. 45C is an example of a wristband-type display device. A portabledisplay device 7100 includes a housing 7101, a display portion 7102,operation buttons 7103, and a transceiver 7104.

The portable display device 7100 can receive a video signal with thetransceiver 7104 and can display the received video on the displayportion 7102. In addition, with the transceiver 7104, the portabledisplay device 7100 can send an audio signal to another receivingdevice.

With the operation button 7103, power ON/OFF, switching displayedvideos, adjusting volume, and the like can be performed.

Here, the display portion 7102 includes the display device of oneembodiment of the present invention. Thus, the portable display devicecan have a curved display portion and high reliability.

FIGS. 45D to 45F show examples of lighting devices. Lighting devices7200, 7210, and 7220 each include a stage 7201 provided with anoperation switch 7203 and a light-emitting portion supported by thestage 7201.

The lighting device 7200 illustrated in FIG. 45D includes alight-emitting portion 7202 with a wave-shaped light-emitting surfaceand thus is a good-design lighting device.

A light-emitting portion 7212 included in the lighting device 7210illustrated in FIG. 45E has two convex-curved light-emitting portionssymmetrically placed. Thus, light radiates from the lighting device 7210in all directions.

The lighting device 7220 illustrated in FIG. 45F includes aconcave-curved light-emitting portion 7222. This is suitable forilluminating a specific range because light emitted from thelight-emitting portion 7222 is collected to the front of the lightingdevice 7220.

The light-emitting portion included in each of the lighting devices7200, 7210, and 7220 is flexible; thus, the light-emitting portion canbe fixed on a plastic member, a movable frame, or the like so that anemission surface of the light-emitting portion can be curved freelydepending on the intended use.

The light-emitting portions included in the lighting devices 7200, 7210,and 7220 each include the display device of one embodiment of thepresent invention. Thus, the light-emitting portions can be curved orbent into any shape and the lighting devices can have high reliability.

FIG. 46A shows an example of a portable display device. A display device7300 includes a housing 7301, a display portion 7302, operation buttons7303, a display portion pull 7304, and a control portion 7305.

The display device 7300 includes the rolled flexible display portion7302 in the cylindrical housing 7301.

The display device 7300 can receive a video signal with the controlportion 7305 and can display the received video on the display portion7302. In addition, a power storage device is included in the controlportion 7305. Moreover, a connector may be included in the controlportion 7305 so that a video signal or power can be supplied directly.

With the operation buttons 7303, power ON/OFF, switching of displayedvideos, and the like can be performed.

FIG. 46B illustrates a state where the display portion 7302 is pulledout with the display portion pull 7304. Videos can be displayed on thedisplay portion 7302 in this state. Furthermore, the operation buttons7303 on the surface of the housing 7301 allow one-handed operation.

Note that a reinforcement frame may be provided for an edge of thedisplay portion 7302 in order to prevent the display portion 7302 frombeing curved when pulled out.

Note that in addition to this structure, a speaker may be provided forthe housing so that sound is output with an audio signal receivedtogether with a video signal.

The display portion 7302 includes the display device of one embodimentof the present invention. Thus, the display portion 7302 is a displaydevice which is flexible and highly reliable, which makes the displaydevice 7300 lightweight and highly reliable.

FIGS. 47A and 47B show a double foldable tablet terminal 9600 as anexample. FIG. 47A illustrates the tablet terminal 9600 which isunfolded. The tablet terminal 9600 includes a housing 9630, a displayportion 9631, a display mode switch 9626, a power switch 9627, apower-saving mode switch 9625, a clasp 9629, and an operation switch9628.

The housing 9630 includes a housing 9630 a and a housing 9630 b, whichare connected with a hinge portion 9639. The hinge portion 9639 makesthe housing 9630 double foldable.

The display portion 9631 is provided on the housing 9630 a, the housing9630 b, and the hinge portion 9639. By the use of the display devicedisclosed in this specification and the like for the display portion9631, the tablet terminal in which the display portion 9631 is foldableand which has high reliability can be provided.

Part of the display portion 9631 can be a touchscreen region 9632 anddata can be input when a displayed operation key 9638 is touched. Astructure can be employed in which half of the display portion 9631 hasonly a display function and the other half has a touchscreen function.The whole display portion 9631 may have a touchscreen function. Forexample, keyboard buttons may be displayed on the entire region of thedisplay portion 9631 so that the display portion 9631 can be used as adata input terminal.

The display mode switch 9626 can switch the display between a portraitmode and a landscape mode, and between monochrome display and colordisplay, for example. The power-saving mode switch 9625 can controldisplay luminance in accordance with the amount of external light in useof the tablet terminal detected by an optical sensor incorporated in thetablet terminal. Another detection device including a sensor fordetecting inclination, such as a gyroscope or an acceleration sensor,may be incorporated in the tablet terminal, in addition to the opticalsensor.

FIG. 47B illustrates the tablet terminal 9600 which is folded. Thetablet terminal 9600 includes the housing 9630, a solar cell 9633, and acharge and discharge control circuit 9634. As an example, FIG. 47Billustrates the charge and discharge control circuit 9634 including abattery 9635 and a DC-to-DC converter 9636.

By including the display device of one embodiment of the presentinvention, the display portion 9631 is foldable. Since the tabletterminal 9600 is double foldable, the housing 9630 can be closed whenthe tablet terminal is not in use, for example; thus, the tabletterminal is highly portable. Moreover, since the display portion 9631can be protected when the housing 9630 is closed, the tablet terminalcan have high durability and high reliability for long-term use.

The tablet terminal illustrated in FIGS. 47A and 47B can have otherfunctions such as a function of displaying various kinds of data (e.g.,a still image, a moving image, and a text image), a function ofdisplaying a calendar, a date, the time, or the like on the displayportion, a touch-input function of operating or editing the datadisplayed on the display portion by touch input, and a function ofcontrolling processing by various kinds of software (programs).

The solar cell 9633 provided on a surface of the tablet terminal cansupply power to the touchscreen, the display portion, a video signalprocessing portion, or the like. Note that the solar cell 9633 ispreferably provided on one or both surfaces of the housing 9630, inwhich case the battery 9635 can be charged efficiently. When a lithiumion battery is used as the battery 9635, there is an advantage ofdownsizing or the like.

The structure and operation of the charge and discharge control circuit9634 illustrated in FIG. 47B is described with reference to a blockdiagram of FIG. 47C. FIG. 47C illustrates the solar cell 9633, thebattery 9635, the DC-to-DC converter 9636, a converter 9637, switchesSW1 to SW3, and the display portion 9631. The battery 9635, the DC-to-DCconverter 9636, the converter 9637, and the switches SW1 to SW3correspond to the charge and discharge control circuit 9634 illustratedin FIG. 47B.

First, description is made on an example of the operation in the casewhere power is generated by the solar cell 9633 with the use of externallight. The voltage of the power generated by the solar cell is raised orlowered by the DC-to-DC converter 9636 so as to be voltage for chargingthe battery 9635. Then, when power from the solar cell 9633 is used forthe operation of the display portion 9631, the switch SW1 is turned onand the voltage of the power is raised or lowered by the converter 9637so as to be voltage needed for the display portion 9631. When images arenot displayed on the display portion 9631, the switch SW1 is turned offand the switch SW2 is turned on so that the battery 9635 is charged.

Although the solar cell 9633 is described as an example of a powergeneration unit, the power generation unit is not particularly limited,and the battery 9635 may be charged by another power generation unitsuch as a piezoelectric element or a thermoelectric conversion element(Peltier element). For example, the battery 9635 may be charged using anon-contact power transmission module that transmits and receives powerwirelessly (without contact) or using another charge unit incombination.

It is needless to say that one embodiment of the present invention isnot limited to the above-described electronic devices and lightingdevices as long as the display device of one embodiment of the presentinvention is included.

FIGS. 48A to 48C illustrate a foldable portable information terminal9310 as an example of an electronic device. FIG. 48A illustrates theportable information terminal 9310 that is opened. FIG. 48B illustratesthe portable information terminal 9310 that is being opened or beingfolded. FIG. 48C illustrates the portable information terminal 9310 thatis folded. The portable information terminal 9310 includes a displaypanel 9316, housings 9315, and hinges 9313. The portable informationterminal 9310 is highly portable when folded. When the portableinformation terminal 9310 is opened, a seamless large display region isobtained; thus, the display image is highly browsable.

The display panel 9316 included in the portable information terminal9310 is supported by the three housings 9315 joined together by thehinges 9313. The display panel 9316 can be folded at the hinges 9313.The portable information terminal 9310 can be reversibly changed inshape from an opened state to a folded state. The display device of oneembodiment of the present invention can be used for the display panel9316. For example, a display device that can be bent with a radius ofcurvature of greater than or equal to 1 mm and less than or equal to 150mm can be used. The display panel 9316 may include a touch sensor.

Note that in one embodiment of the present invention, a sensor thatsenses whether the display panel 9316 is in a folded state or anunfolded state may be used. The operation of a folded portion (or aportion that becomes invisible by a user by folding) of the displaypanel 9316 may be stopped by a control device through the acquisition ofdata indicating the folded state of the touch panel. Specifically,display of the portion may be stopped. In the case where a touch sensoris included, detection by the touch sensor may be stopped.

Similarly, the control device of the display panel 9316 may acquire dataindicating the unfolded state of the display panel 9316 to resumedisplaying and sensing by the touch sensor.

FIGS. 48D and 48E each illustrate a foldable portable informationterminal 9320. FIG. 48D illustrates the portable information terminal9320 that is folded so that a display portion 9322 is on the outside.FIG. 48E illustrates the portable information terminal 9320 that isfolded so that the display portion 9322 is on the inside. When theportable information terminal 9320 is not used, the portable informationterminal 9320 is folded so that a non-display portion 9325 faces theoutside, whereby the display portion 9322 can be prevented from beingcontaminated or damaged. The display device of one embodiment of thepresent invention can be used for the display portion 9322.

FIG. 48F is a perspective view illustrating an external shape of aportable information terminal 9330. FIG. 48G is a top view of theportable information terminal 9330. FIG. 48H is a perspective viewillustrating an external shape of a portable information terminal 9340.

The portable information terminals 9330 and 9340 each function as, forexample, one or more of a telephone set, a notebook, and an informationbrowsing system. Specifically, the portable information terminals 9330and 9340 each can be used as a smartphone.

The portable information terminals 9330 and 9340 can display charactersand image information on their plurality of surfaces. For example, oneor more operation buttons 9339 can be displayed on the front surface(FIG. 48F). In addition, information 9337 indicated by dashed rectanglescan be displayed on the top surface (FIG. 48G) or on the side surface(FIG. 48H). Examples of the information 9337 include notification from asocial networking service (SNS), display indicating reception of ane-mail or an incoming call, the title of an e-mail or the like, thesender of an e-mail or the like, the date, the time, remaining battery,and the reception strength of an antenna. Alternatively, the operationbuttons 9339, an icon, or the like may be displayed in place of theinformation 9337. Although FIGS. 48F and 48G illustrate an example inwhich the information 9337 is displayed at the top and side surfaces,one embodiment of the present invention is not limited thereto. Theinformation 9337 may be displayed, for example, on the bottom or rearsurface.

For example, a user of the portable information terminal 9330 can seethe display (here, the information 9337) with the portable informationterminal 9330 put in a breast pocket of his/her clothes.

Specifically, a caller's phone number, name, or the like of an incomingcall is displayed on the front surface of the portable informationterminal 9330. Thus, the user can see the display without taking out theportable information terminal 9330 from the pocket and decide whether toanswer the call.

The display device of one embodiment of the present invention can beused for a display portion 9333 mounted in each of a housing 9335 of theportable information terminal 9330 and a housing 9336 of the portableinformation terminal 9340. One embodiment of the present invention canprovide a highly reliable display device having a curved display portionwith a high yield.

As in a portable information terminal 9345 illustrated in FIG. 48I, datamay be displayed on three or more surfaces. Here, data 9355, data 9356,and data 9357 are displayed on different surfaces.

The display device of one embodiment of the present invention can beused for a display portion 9358 included in a housing 9354 of theportable information terminal 9345. One embodiment of the presentinvention can provide a highly reliable display device having a curveddisplay portion with a high yield.

FIG. 49A illustrates an automobile 9700. FIG. 49B illustrates a driver'sseat of the automobile 9700. The automobile 9700 includes a car body9701, wheels 9702, a dashboard 9703, lights 9704, and the like. Thedisplay device of one embodiment of the present invention can be used ina display portion or the like of the automobile 9700. For example, thedisplay device of one embodiment of the present invention can be used indisplay portions 9710 to 9715 illustrated in FIG. 49B.

The display portion 9710 and the display portion 9711 are provided in anautomobile windshield. The display device of one embodiment of thepresent invention can be a see-through display device, through which theopposite side can be seen, by using a light-transmitting conductivematerial for its electrodes. Such a see-through display device does nothinder driver's vision during driving the automobile 9700. Therefore,the display device of one embodiment of the present invention can beprovided in the windshield of the automobile 9700. Note that in the casewhere a transistor or the like for driving the display device isprovided in the display device, a transistor having light-transmittingproperties, such as an organic transistor using an organic semiconductormaterial or a transistor using an oxide semiconductor, is preferablyused.

The display portion 9712 is provided on a pillar portion. For example,an image taken by an imaging unit provided in the car body is displayedon the display portion 9712, whereby the view hindered by the pillarportion can be compensated. The display portion 9713 is provided on thedashboard. For example, an image taken by an imaging unit provided inthe car body is displayed on the display portion 9713, whereby the viewhindered by the dashboard can be compensated. That is, by displaying animage taken by an imaging unit provided on the outside of theautomobile, blind areas can be eliminated and safety can be increased.Displaying an image to compensate for the area which a driver cannotsee, makes it possible for the driver to confirm safety easily andcomfortably.

The display portion 9714 and the display portion 9715 can provide avariety of kinds of information such as navigation data, a speedometer,a tachometer, a mileage, a fuel meter, a gearshift indicator, andair-condition setting. The content, layout, or the like of the displayon the display portions can be changed freely by a user as appropriate.The information listed above can also be displayed on the displayportions 9710 to 9713. The display portions 9710 to 9715 can also beused as lighting devices.

This embodiment can be implemented in an appropriate combination withany of the structures described in the other embodiments.

This application is based on Japanese Patent Application serial no.2014-091849 filed with Japan Patent Office on Apr. 25, 2014 and JapanesePatent Application serial no. 2014-095018 filed with Japan Patent Officeon May 2, 2014, the entire contents of which are hereby incorporated byreference.

What is claimed is:
 1. A display device comprising: a first substrate; asecond substrate; a display element; a touch sensor; a transistor; afirst electrode; an insulating layer; a second electrode; a firstexternal electrode; and a second external electrode, wherein the firstsubstrate and the second substrate overlap with each other with thedisplay element, the touch sensor, the transistor, the first electrode,the insulating layer, and the second electrode positioned therebetween,wherein the first electrode is configured to supply a signal to thetransistor, wherein the transistor is configured to supply a signal tothe display element, wherein the second electrode is configured tosupply a signal to the touch sensor, wherein the second substrate isprovided between the first external electrode and the first electrode,wherein the second substrate is provided between the second externalelectrode and the second electrode, wherein the first electrode iselectrically connected to the first external electrode through anopening in the second substrate, and wherein the second electrode iselectrically connected to the second external electrode through anopening in the insulating layer and the opening in the second substrate.2. The display device according to claim 1, wherein the first substrateand the second substrate are flexible substrates.
 3. The display deviceaccording to claim 1, wherein the display element is a light-emittingelement.
 4. The display device according to claim 1, wherein the touchsensor is a capacitive touch sensor.
 5. The display device according toclaim 1, wherein the touch sensor is an active matrix touch sensor. 6.The display device according to claim 1, wherein the first electrode andthe second electrode comprise tungsten.
 7. An electronic devicecomprising: the display device according to claim 1; and a hinge.
 8. Adisplay device comprising: a first substrate; a second substrate; adisplay element; a touch sensor; a transistor; a first electrode; asecond electrode; a first external electrode; and a second externalelectrode, wherein the first substrate and the second substrate overlapwith each other with the display element, the touch sensor, the firstelectrode, and the second electrode positioned therebetween, wherein thefirst electrode is configured to supply a signal to the transistor,wherein the transistor is configured to supply a signal to the displayelement, wherein the second electrode is configured to supply a signalto the touch sensor, wherein the second substrate is provided betweenthe second external electrode and the second electrode, wherein thefirst electrode is electrically connected to the first externalelectrode through a first opening in the second substrate, and whereinthe second electrode is electrically connected to the second externalelectrode through a second opening in the second substrate.
 9. Thedisplay device according to claim 8, wherein the first substrate and thesecond substrate are flexible substrates.
 10. The display deviceaccording to claim 8, wherein the display element is a light-emittingelement.
 11. The display device according to claim 8, wherein the touchsensor is a capacitive touch sensor.
 12. The display device according toclaim 8, wherein the touch sensor is an active matrix touch sensor. 13.The display device according to claim 8, wherein the first electrode andthe second electrode comprise tungsten.
 14. An electronic devicecomprising: the display device according to claim 8; and a hinge.